Change dialogdescription for renaming group block

[masteradhoc]

Fixes #54346

What?

@t-hamano made a good point i also noticed while testing. we should precise the popup message for the renaming introduced in #53735

Why?

Be more precise. there is nothing to be choosen you have to enter the text as you want :)

How?

Changing the text inserted in code.

Testing Instructions

1. New Post (or enter the Site Editor)
2. Add some blocks and then Group them.
3. Open List View
4. Now open the block options menu (either via List View or via the block in the canvas) and click Rename.
5. Check message above field

Testing Instructions for Keyboard

Screenshots or screencast

[t-hamano]

Thanks for the PR, @masteradhoc!

I think this change makes sense, but would like to hear from @getdave, @richtabor, @andrewserong who were involved in #53735 🙏

[alexstine]

Giving this approve as it is more clear in English. Interested to hear other opinions.

[getdave]

Makes sense to me. Thank you.

[t-hamano]

Thank you everyone, now let's merge this PR.

@masteradhoc Thank you for your contribution!