Minor contributor docs update (#7948)

- Fixing Link
- Clarify that no-force-push applies to Pull Requests, too.

substrate/docs/CONTRIBUTING.adoc

@@ -10,11 +10,11 @@ Individuals making significant and valuable contributions are given commit-acces
 
 There are a few basic ground-rules for contributors (including the maintainer(s) of the project):
 
-. **No `--force` pushes** or modifying the master branch history in any way. If you need to rebase, ensure you do it in your own repo.
+. **No `--force` pushes** or modifying the master branch history in any way. If you need to rebase, ensure you do it in your own repo. No rewriting of the history after the code has been shared (e.g. through a Pull-Request).
 . **Non-master branches**, prefixed with a short name moniker (e.g. `gav-my-feature`) must be used for ongoing work.
 . **All modifications** must be made in a **pull-request** to solicit feedback from other contributors.
 . A pull-request *must not be merged until CI* has finished successfully.
-. Contributors should adhere to the ./STYLE_GUIDE.md[house coding style].
+. Contributors should adhere to the link:STYLE_GUIDE.md[house coding style].
 
 
 == Merge Process