UI: Update theme to match Shader nodes category color with socket color

The change to match socket color and category was already done, but it was missing
versioning code to update the theme on load.

Fixes T83500 (already closed as invalid, but this would solve the non-matching colors)

Reviewed by Hans Goudey (HooglyBoogly)

source/blender/blenkernel/BKE_blender_version.h

@@ -39,7 +39,7 @@ extern "C" {
 
 /* Blender file format version. */
 #define BLENDER_FILE_VERSION BLENDER_VERSION
-#define BLENDER_FILE_SUBVERSION 5
+#define BLENDER_FILE_SUBVERSION 6
 
 /* Minimum Blender version that supports reading file written with the current
  * version. Older Blender versions will test this and show a warning if the file

source/blender/blenloader/intern/versioning_userdef.c

@@ -255,6 +255,10 @@ static void do_versions_theme(const UserDef *userdef, bTheme *btheme)
     FROM_DEFAULT_V4_UCHAR(space_node.nodeclass_attribute);
   }
 
+  if (!USER_VERSION_ATLEAST(292, 6)) {
+    FROM_DEFAULT_V4_UCHAR(space_node.nodeclass_shader);
+  }
+
   /**
    * Versioning code until next subversion bump goes here.
    *