Inclusive language changes for sp_BlitzIndex

[VladDBA]

Hey Brent!

I've updated the wording in sp_BlitzIndex for:

• Findings
• Findings Groups
• Debug messages

I've also updated the list in sp_BlitzIndex_Checks_by_Priority.md

Note that I couldn't find check_id 12 anywhere in sp_BlitzIndex nor anything else pointing to "Aggressive Indexes" aside from check_id 11,

Closes #3571

[BrentOzar]

Thanks for the pull request! I really appreciate how much work this was. Looks good, works on my machines, merging into the dev branch, will be in the next release with credit to you in the release notes.