`get_block_file_template()` incorrectly documented

[peterwilsoncc]

The function get_block_file_template() is currently incorrectly documented with get_block_template()'s docblock.

The former is used as a fallback by the latter when no templates are found in the database.

The pre_get_block_file_template filter within get_block_file_template() is similarly incorrectly documented.

[SergeyBiryukov]

Introduced in [52062] / #54335.

This PR adjusts get_block_file_template() documentation per 55929

Trac ticket: https://core.trac.wordpress.org/ticket/55929

[felipeelia]

@peterwilsoncc the PR above addresses those changes and also adjusts the description of the 'get_block_file_template' filter a bit. If any adjustment in the text is needed, please let me know. Thanks!

[peterwilsoncc]

Thanks @felipeelia, I've self-assigned this for review. As it's a docs change it can be committed at any time during the cycle so isn't affected by the beta 1 deadline this week.

[peterwilsoncc]

The linked pull request is approved for commit as of ​fee956a.

[peterwilsoncc]

In 54380:

Docs: Correct docblocks for get_block_file_template().

This corrects the docblock for get_block_file_template() and the filters it contains: pre_get_block_file_template and get_block_file_template.

Prior to this change they were incorrectly documented with the docblocks for get_block_template() and its associated filters.

Props felipeelia.
Fixes #55929.

Merged in https://core.trac.wordpress.org/changeset/54380 / ​https://github.com/WordPress/wordpress-develop/commit/2b2f1fd885a6bf948ef5ca83229951f59ceea99d