ci: update commit range to check

For the release branch, update the makefile `check-commits` rule to check the
new commits on the release branch.

Signed-off-by: Christian Hopps <[email protected]>

Author: choppsv1

Makefile

@@ -12,7 +12,7 @@ tests:
 format:
 	tox -e format
 
-LYPY_COMMIT_RANGE ?= origin/master..
+LYPY_COMMIT_RANGE ?= origin/b_3.x..
 
 check-commits:
 	./check-commits.sh $(LYPY_COMMIT_RANGE)