Bump version to 3.38.1

We will need to bump the version differently for GNOME 40. In the
meantime, just increment the micro version.

README.md

 gedit - The GNOME text editor
 =============================
 
-This is version 3.38.0 of gedit.
+This is version 3.38.1 of gedit.
 
 gedit is the text editor of the GNOME desktop environment.
 

meson.build

 project(
   'gedit', 'c',
-  version: '3.38.0',
+  version: '3.38.1',
   meson_version: '>= 0.53'
 )