Upgrade/Install: Make `WP_Filesystem_FTPext::size()` return `false` on failure.

While `WP_Filesystem_Base::size()` is documented to return `false` on failure, `ftp_size()` returns -1, and the method documentation was recently updated to reflect that.

This commit restores the previous `@return` tag and corrects the actual return value instead, to bring consistency with all the other `WP_Filesystem_*::size()` methods:
* `WP_Filesystem_Base::size()`
* `WP_Filesystem_Direct::size()`
* `WP_Filesystem_ftpsockets::size()`
* `WP_Filesystem_SSH2::size()`
{{{
@return int|false Size of the file in bytes on success, false on failure.
}}}

This better matches the purpose of the API to provide a consistent interface for various filesystem implementations.

Follow-up to [6779], [30678], [45226], [53860], [53862].

Fixes #51170.
Built from https://develop.svn.wordpress.org/trunk@53898


git-svn-id: http://core.svn.wordpress.org/trunk@53457 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-filesystem-ftpext.php

@@ -510,14 +510,14 @@ class WP_Filesystem_FTPext extends WP_Filesystem_Base {
 	 * Gets the file size (in bytes).
 	 *
 	 * @since 2.5.0
-	 * @since 6.1.0 Corrected the return value: while WP_Filesystem_Base::size()
-	 *              is documented to return false on failure, ftp_size() returns -1.
 	 *
 	 * @param string $file Path to file.
-	 * @return int Size of the file in bytes on success, -1 on failure.
+	 * @return int|false Size of the file in bytes on success, false on failure.
 	 */
 	public function size( $file ) {
-		return ftp_size( $this->link, $file );
+		$size = ftp_size( $this->link, $file );
+
+		return ( $size > -1 ) ? $size : false;
 	}
 
 	/**

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '6.1-alpha-53897';
+$wp_version = '6.1-alpha-53898';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.