Auto merge of rust-lang#13927 - lnicola:rm-blank-issue, r=lnicola

minor: tweak wording and remove blank issue template

There's already a "blank issue" link at the bottom, and some users seem to pick this one because it's the first.

Author: bors

.github/ISSUE_TEMPLATE/blank_issue.md

@@ -22,4 +22,4 @@ Otherwise please try to provide information which will help us to fix the issue
 
 **rustc version**: (eg. output of `rustc -V`)
 
-**relevant settings**: (eg. client settings, or environment variables like `CARGO`, `RUSTUP_HOME` or `CARGO_HOME`)
+**relevant settings**: (eg. client settings, or environment variables like `CARGO`, `RUSTC`, `RUSTUP_HOME` or `CARGO_HOME`)