run_tests: only allow help2man skipping in CI

Make sure we run this for local devs.

Change-Id: I472b7c347086d54649dd9d5778eea4737447b353
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/471921
Tested-by: Mike Frysinger <vapier@google.com>
Reviewed-by: Scott Lee <ddoman@google.com>
Commit-Queue: Mike Frysinger <vapier@google.com>

run_tests

diff --git a/run_tests b/run_tests
index ea34e67..9a8fad3 100755
--- a/run_tests
+++ b/run_tests
@@ -104,7 +104,8 @@
 
 def run_update_manpages() -> int:
     """Returns the exit code from release/update-manpages."""
-    if not shutil.which("help2mafn"):
+    # Allow this to fail on CI, but not local devs.
+    if is_ci() and not shutil.which("help2man"):
         print("update-manpages: help2man not found; skipping test")
         return 0