Remove the diagram of all outputs generated by x.py

These are already present in the table below, there's no need to repeat it.
Having it near the middle of the page makes it feel more overwhelming.

Author: jyn514

src/building/bootstrapping.md

@@ -229,14 +229,6 @@ another program we are building with the stage N compiler:
 `build --stage N compiler/rustc` is linking the stage N artifacts to the `std`
 built by the stage N compiler.
 
-Here is a chart of a full build using `x.py`:
-
-<img alt="A diagram of the rustc compilation phases" src="../img/rustc_stages.svg" class="center" />
-
-Keep in mind this diagram is a simplification, i.e. `rustdoc` can be built at
-different stages, the process is a bit different when passing flags such as
-`--keep-stage`, or if there are non-host targets.
-
 ### Stages and `std`
 
 Note that there are two `std` libraries in play here: