build(dev): Do not restrict using latest version of pip (#23775)

Unfortunately, the latest change has not been playing nicely for me
and folks using Python 3.6

Makefile

@@ -68,7 +68,7 @@ ensure-venv:
 	@./scripts/ensure-venv.sh
 
 ensure-pinned-pip: ensure-venv
-	$(PIP) install --no-cache-dir --upgrade "pip>=20.0.2,<20.3"
+	$(PIP) install --no-cache-dir --upgrade "pip>=20.0.2"
 
 setup-git-config:
 	@git config --local branch.autosetuprebase always