Bug 32226: Fix capitalization of "Add/Edit html content"

Bug 32226: Fix capitalization of "Add/Edit html content"

HTML is an abbreviation and as such should always be
capitalized.

To test:
* Go to administration > libraries
* Edit any existing branch
* The hint for OPAC info reads 'Add html content'
* Add some content, verify the link changes to 'Edit html content'
* Apply patch
* Verify both cases now read 'HTML'

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>