Remove spurious reference to .cpp extension

Bug: none
Change-Id: I6e817bba8bc374bf542a3eaff2abd7c390602064
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/350565
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#42328}
diff --git a/g3doc/style-guide.md b/g3doc/style-guide.md
index 6822fdf..ead633a 100644
--- a/g3doc/style-guide.md
+++ b/g3doc/style-guide.md
@@ -55,7 +55,7 @@
   test `.cc` files, and with `.cc` files that define `main`.)
 
 See also the
-[examples and exceptions on how to treat `.h` and `.cpp` files](style-guide/h-cc-pairs.md).
+[examples and exceptions on how to treat `.h` and `.cc` files](style-guide/h-cc-pairs.md).
 
 This makes the source code easier to navigate and organize, and precludes some
 questionable build system practices such as having build targets that don't pull