Letting the clock tick without a reason introduces the
possibility of nondeterministic test failures depending on the execution
time. The default value when not specified is tick=True, which makes it
easy to miss.
The rule doesn't prohibit setting tick=True, as perhaps there will be
tests wanting to use that feature on purpose, but such a test should
explicitly set it to make the intent clear.
Semgrep 0.118.0 changed the default of --scan-unknown-extensions to
false. It also seems that it no longer respects --lang (or never
did), so rename the config file to reflect that it only includes
Python rules, to make it clear that additional languages will require
separate config files.
Signed-off-by: Anders Kaseorg <anders@zulip.com>