fix(which_key): only get telescope mappings

[fdschmidt93]

Description

Change action_utils.get_registered_mappings to only capture mappings attached to prompt via telescope interfaces, as the interface would break otherwise currently anyway (and it's unclear whether other mappings should be showing up.. because then you'd attach them via telescope).

Fixes #2087

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• Having installed nvim-surround (and reproduce with original issue)
• Observing no errors

Configuration:

See above

Checklist:

• My code follows the style guidelines of this project (stylua)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas