pw_protobuf: Tweak documentation of name conflicts
pw_protobuf: Tweak documentation of name conflicts

Rearrange and reword part of the "Reserved-Word Conflicts" section of
docs.rst for better clarity and readability.

Change-Id: I198ff8029c2614f12599445519b379397018c5a2
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/99004
Reviewed-by: Ted Pudlik <c7372cc3e451acc046049fca9e050bcb2a4a3d11@google.com>
Commit-Queue: Matthias Guenther <aebfab562a30dd63c351a5f7362e95fd963f583b@google.com>

google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed,google/pigweed