Remove redundant ignore-tidy-linelength annotations

This is step 2 towards fixing #77548.

In the codegen and codegen-units test suites, the `//` comment markers
were kept in order not to affect any source locations. This is because
these tests cannot be automatically `--bless`ed.

src/test/codegen/remap_path_prefix/main.rs

@@ -1,5 +1,5 @@
 // ignore-windows
-// ignore-tidy-linelength
+//
 
 // compile-flags: -g  -C no-prepopulate-passes --remap-path-prefix={{cwd}}=/the/cwd --remap-path-prefix={{src-base}}=/the/src
 // aux-build:remap_path_prefix_aux.rs