docs: update contributing guide to rebase of origin/master not local master branch

Updating the squash command to reference origin/master instead of the local master branch in the event a local environment's master branch is not up to date.

CONTRIBUTING.md

@@ -72,7 +72,7 @@ Here is a quick tip to squash all commits for a branch named `test`:
 
 ```
 git checkout test
-git reset $(git merge-base master $(git rev-parse --abbrev-ref HEAD))
+git reset $(git merge-base origin/master $(git rev-parse --abbrev-ref HEAD))
 git add -A
 git commit -m "feat: example conventional commit"
 git push --force