Coding Standards: Use `implode` instead of `join` in wp-includes/fonts/class-wp-font-utils.php

[david.binda]

r49193 replaced multiple instances of aliased functions by the canonical ones.

r57539 contains an instance of join, which, IMHO, should be replaced for implode (per r49193).

[hellofromTonya]

Good catch @davidbinda. Yes, I agree with you. Marking this for commit and will prep the commit shortly.

Here's the PR in Gutenberg with the same change to keep the code in sync ​https://github.com/WordPress/gutenberg/pull/58845.

[hellofromTonya]

In 57567:

Coding Standards: Replace alias join() in WP_Font_Utils.

Replaces the alias join() with its canonical implode().

Using the canonical function name for PHP functions is strongly recommended, as aliases may be deprecated or removed without (much) warning.

Follow-up to [57539], [49193].

Props davidbinda.
Fixes #60473.