Fix a typo in the C++ style guide.

Bug: 1343840
Change-Id: I4cad93cf15f2fef912f9f956f3c784ce6d3f1f9d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3760388
Commit-Queue: Joseph Koshy <jkoshy@google.com>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1023732}

styleguide/c++/c++.md

@@ -36,7 +36,7 @@ status of Chromium's C++ support is covered in more detail in
 
   * Functions used only for testing should be restricted to test-only usages
     with the testing suffixes supported by
-    [PRESUMBIT.py](https://chromium.googlesource.com/chromium/src/+/main/PRESUBMIT.py).
+    [PRESUBMIT.py](https://chromium.googlesource.com/chromium/src/+/main/PRESUBMIT.py).
     `ForTesting` is the conventional suffix although similar patterns, such as
     `ForTest`, are also accepted. These suffixes are checked at presubmit time
     to ensure the functions are called only by test files.