Stop mentioning that flex can install specific symfony version

[ostrolucky]

... it doesn't. Skeleton uses carets for specifying versions

[javiereguiluz]

I can't reproduce this issues. The following commands worked for me and do what you expect from them:

composer create-project symfony/skeleton my-project "3.3.*"
composer create-project symfony/skeleton my-project "3.4.*"
...

I propose to close this pull request then, but in #8976 I'm proposing some rewords in this section. Thanks!

[ostrolucky]

It really doesn't. As you see I specified 3.3 version, but it downloads 3.4+ components

➜  Documents composer create-project symfony/skeleton my-project "3.3.*"
Installing symfony/skeleton (v3.3.11)
  - Installing symfony/skeleton (v3.3.11)
    Downloading: 100%         

Created project in my-project
Loading composer repositories with package information
Updating dependencies (including require-dev)
  - Installing symfony/flex (v1.0.57)
    Loading from cache


Prefetching 3 packages 🎶
  - Connecting (100%)
  - Downloading (100%)

  - Installing psr/log (1.0.2)
    Loading from cache

  - Installing symfony/debug (v3.4.2)
    Loading from cache

  - Installing symfony/polyfill-mbstring (v1.6.0)
    Loading from cache

  - Installing symfony/console (v3.4.2)
    Loading from cache

  - Installing symfony/routing (v3.4.2)
    Loading from cache

  - Installing symfony/yaml (v3.4.2)
    Loading from cache

  - Installing symfony/framework-bundle (v3.4.2)
    Loading from cache

  - Installing symfony/http-foundation (v3.4.2)
    Loading from cache

  - Installing symfony/event-dispatcher (v3.4.2)
    Loading from cache

  - Installing symfony/http-kernel (v3.4.2)
    Loading from cache

  - Installing symfony/finder (v3.4.2)
    Loading from cache

  - Installing symfony/filesystem (v3.4.2)
    Loading from cache

  - Installing psr/container (1.0.0)
    Loading from cache

  - Installing symfony/dependency-injection (v3.4.2)
    Loading from cache

  - Installing symfony/config (v3.4.2)
    Loading from cache

  - Installing symfony/class-loader (v3.4.2)
    Loading from cache

  - Installing psr/simple-cache (1.0.0)
    Loading from cache

  - Installing psr/cache (1.0.1)
    Loading from cache

  - Installing symfony/polyfill-apcu (v1.6.0)
    Loading from cache

  - Installing symfony/cache (v3.4.2)
    Loading from cache

  - Installing symfony/dotenv (v3.4.2)
    Loading from cache

Writing lock file
Generating autoload files
Symfony operations: 4 recipes (c3001f755a56d8c176c45819a920c814)
  - Configuring symfony/flex (>=1.0): From github.com/symfony/recipes:master
  - Configuring symfony/framework-bundle (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/console (>=3.3): From github.com/symfony/recipes:master
  - Configuring symfony/routing (>=3.3): From github.com/symfony/recipes:master
Executing script cache:clear [OK]
Executing script assets:install --symlink --relative public [OK]

Some files may have been created or updated to configure your new packages.
Don't hesitate to review, edit and commit them: these files are yours.

              
 What's next? 
              

  * Run your application:
    1. Change to the project directory
    2. Execute the php -S 127.0.0.1:8000 -t public command;
    3. Browse to the http://localhost:8000/ URL.

       Quit the server with CTRL-C.
       Run composer require server for a better web server.

  * Read the documentation at https://symfony.com/doc

➜  Documents

[javiereguiluz]

@ostrolucky you are right! I'm sorry for not having properly reviewed this. I've updated #8976 to just remove this entire section. You can't install specific branch versions with a single command when using Flex, so let's not mention it. The installation of beta and RC versions is covered in other articles, so we're not missing anything by removing this. Thanks!