Issue/uppercase thousands suffix

[khaykov]

In this PR we are uppercasing an English suffix for 1000 (k > K) to align with iOS, as mentioned here. That string is translatable, so other locales could use an appropriate suffix.

The suffix will be changed in the stats and unread posts counter.

In addition, I removed the unneeded has() check, that was mentioned here.

To test:

• You can check the new uppercase suffix in Stats (for values > 9999) or in unread posts count (if you have enough posts).

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[peril-wordpress-mobile]

You can trigger optional UI/connected tests for these changes by visiting CircleCI here.

[peril-wordpress-mobile]

You can test the changes on this Pull Request by downloading the APK here.

[develric]

Thanks for the PR @khaykov , works as described 👍 .