[clang-tools-extra] [clang-tidy] Rename `google-readability-casting` to `modernize-avoid-c-style-cast` (PR #171058)

[Baranov Victor via cfe-commits]

================
@@ -3,12 +3,10 @@
 google-readability-casting
 ==========================
 
+The `google-readability-casting` check is an alias, please see 
+:doc:`modernize-avoid-c-style-cast <../modernize/avoid-c-style-cast>` 
+for more information.
+
 Finds usages of C-style casts.
 
 https://google.github.io/styleguide/cppguide.html#Casting
-
-Corresponding cpplint.py check name: `readability/casting`.
----------------
vbvictor wrote:

This `cpplint.py` should be left in `readability-casting.rst` because it is google's tool.

https://github.com/llvm/llvm-project/pull/171058