msglist: Update label to 'Messages with yourself' in DM header

[lakshya1goel]

Fixes: #1319

Screenshot

[chrisbobbe]

i18n: Update label to "Messages with yourself" in DM header

commit-message nit: choose a different prefix than i18n. This commit involves the i18n subsystem, because it's changing a UI string and we translate those—but it isn't a change in the i18n subsystem itself. How about msglist.

[chrisbobbe]

Also, updating the PR title to remove [nfc]—this is a behavior change, not a pure refactor.

[chrisbobbe]

Thanks, LGTM! Marking for Greg's review.

[gnprice]

Thanks for taking care of this! A few small comments.

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There's a TODO comment where this is used:

    } else {
      // TODO pick string; web has glitchy "You and $yourname"
      title = zulipLocalizations.messageListGroupYouWithYourself;

We're taking care of that TODO with this change, so the comment should be deleted.

---

There was a chat thread where we decided to make this change, right? Let's have the commit message link to that thread.

---

In the commit message:

Fixes: zulip#1319

It should say just #1319, not zulip#1319 — the "zulip" part is redundant.

[lakshya1goel]

Thanks for the review @gnprice, pushed the revision, PTAL.

[gnprice]

Thanks for the revision! Looks good; merging.