docs: Correct typo on Contributing page

Change-Id: If4bcfff124159d5ea90e7ad6ad2bdfa8fb0dc5a9
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/96801
Commit-Queue: Michael Hitchens <hitchens@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
diff --git a/docs/contributing.rst b/docs/contributing.rst
index 9d275e0..19b6707 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -194,7 +194,7 @@
 
      pw_foo: Improve use of std::unique_lock
 
-**No**: Uses a non-standard ``[]`` to indicate moduule:
+**No**: Uses a non-standard ``[]`` to indicate module:
 
 .. code:: none