tools: Improve output from check-capitalization.
tools: Improve output from check-capitalization.

Ideally, we'd print line numbers etc., but that's complicated because
the `translation.json` format doesn't include them, and usually it's
easy to find strings because you just added them anyway.

But adding a bit more of a `git grep` hint should help.

Fixes #14321.

zulip/zulip,kou/zulip,hackerkid/zulip,zulip/zulip,kou/zulip,zulip/zulip,punchagan/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,punchagan/zulip,hackerkid/zulip,punchagan/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,andersk/zulip,hackerkid/zulip,hackerkid/zulip,eeshangarg/zulip,kou/zulip,hackerkid/zulip,rht/zulip,andersk/zulip,punchagan/zulip,zulip/zulip,eeshangarg/zulip,rht/zulip,rht/zulip,kou/zulip,punchagan/zulip,andersk/zulip,andersk/zulip,rht/zulip,eeshangarg/zulip,punchagan/zulip,punchagan/zulip,kou/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,andersk/zulip,andersk/zulip,rht/zulip,kou/zulip,zulip/zulip,hackerkid/zulip,rht/zulip