Docs: Update some reusable block references to synced patterns.

In WordPress 6.3, [https://wordpress.org/documentation/article/reusable-blocks/ Reusable Blocks were renamed to Patterns]. A synced pattern will behave in exactly the same way as a reusable block.

This commit updates some references in DocBlocks and inline comments to use the new name.

Follow-up to [56030].

Props benjaminknox, oglekler, hellofromTonya, marybaum, nicolefurlan.
Fixes #59388.

git-svn-id: https://develop.svn.wordpress.org/trunk@57032 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/blocks.php

@@ -659,7 +659,8 @@ function has_blocks( $post = null ) {
  *
  * This test optimizes for performance rather than strict accuracy, detecting
  * whether the block type exists but not validating its structure and not checking
- * reusable blocks. For strict accuracy, you should use the block parser on post content.
+ * synced patterns (formerly called reusable blocks). For strict accuracy,
+ * you should use the block parser on post content.
  *
  * @since 5.0.0
  *