Experimental: Remove gutenberg_initialize_editor (#53527)

`git bisect` revealed that [the last known use of that function](https://github.com/WordPress/gutenberg/pull/47055/files#diff-bb9ee7c63178059379505a610c303b5b11c1bc38b0961ae3cee952c68d897256L110-L118) was in `lib/experimental/navigation-page.php`, which was removed in #47055, alongside a lot of other code. It was probably by oversight that `gutenberg_initialize_editor` was left behind.

lib/experimental/editor-settings.php

@@ -5,73 +5,6 @@
  * @package gutenberg
  */
 
-/**
- * Initialize a block-based editor.
- *
- * @param string $editor_name          Editor name.
- * @param string $editor_script_handle Editor script handle.
- * @param array  $settings {
- *      Elements to initialize a block-based editor.
- *
- *      @type array  $preload_paths        Array of paths to preload.
- *      @type string $initializer_name     Editor initialization function name.
- *      @type array  $editor_settings      Editor settings.
- * }
- * @return void
- */
-function gutenberg_initialize_editor( $editor_name, $editor_script_handle, $settings ) {
-
-	$defaults = array(
-		'preload_paths'    => array(),
-		'initializer_name' => 'initialize',
-		'editor_settings'  => array(),
-	);
-
-	$settings = wp_parse_args( $settings, $defaults );
-
-	/**
-	 * Preload common data by specifying an array of REST API paths that will be preloaded.
-	 *
-	 * Filters the array of paths that will be preloaded.
-	 *
-	 * @param string[] $preload_paths Array of paths to preload.
-	 */
-	$preload_paths = apply_filters( "{$editor_name}_preload_paths", $settings['preload_paths'] );
-
-	$preload_data = array_reduce(
-		$preload_paths,
-		'rest_preload_api_request',
-		array()
-	);
-
-	wp_add_inline_script(
-		'wp-api-fetch',
-		sprintf(
-			'wp.apiFetch.use( wp.apiFetch.createPreloadingMiddleware( %s ) );',
-			wp_json_encode( $preload_data )
-		),
-		'after'
-	);
-	wp_add_inline_script(
-		"wp-{$editor_script_handle}",
-		sprintf(
-			'wp.domReady( function() {
-				wp.%s.%s( "%s", %s );
-			} );',
-			lcfirst( str_replace( '-', '', ucwords( $editor_script_handle, '-' ) ) ),
-			$settings['initializer_name'],
-			str_replace( '_', '-', $editor_name ),
-			wp_json_encode( $settings['editor_settings'] )
-		)
-	);
-
-	// Preload server-registered block schemas.
-	wp_add_inline_script(
-		'wp-blocks',
-		'wp.blocks.unstable__bootstrapServerSideBlockDefinitions(' . wp_json_encode( get_block_editor_server_block_settings() ) . ');'
-	);
-}
-
 /**
  * Sets a global JS variable used to trigger the availability of each Gutenberg Experiment.
  */