docs: decorate method name

Author: kenjis

user_guide_src/source/libraries/files.rst

@@ -92,7 +92,7 @@ By default, the original filename was used. You can specify a new filename by pa
 .. literalinclude:: files/009.php
     :lines: 2-
 
-The move() method returns a new File instance that for the relocated file, so you must capture the result if the
+The ``move()`` method returns a new File instance that for the relocated file, so you must capture the result if the
 resulting location is needed:
 
 .. literalinclude:: files/010.php