Clarify that backtick escaping doesn't work for @bors try jobs

Author: Kobzol

src/doc/rustc-dev-guide/src/tests/ci.md

@@ -151,8 +151,9 @@ which can be used in one of two ways:
 
 Each job pattern can either be an exact name of a job or a glob pattern that matches multiple jobs,
 for example `*msvc*` or `*-alt`. You can start at most 20 jobs in a single try build. When using
-glob patterns, you might want to wrap them in backticks (`` ` ``) to avoid GitHub rendering
-the pattern as Markdown.
+glob patterns in the PR description, you can wrap them in backticks (`` ` ``) to avoid GitHub rendering
+the pattern as Markdown if it contains e.g. an asterisk. Note that this escaping will not work when using
+the `@bors jobs=` parameter.
 
 The job pattern needs to match one or more jobs defined in the `auto` or `optional` sections
 of [`jobs.yml`]: