[gegl] ppm-load: fix file type registration by remove trailing colon

[Øyvind Kolås <ok src gnome org>]

commit cd1e682023faddd210af98e8d5d3e0b500f825b5
Author: Øyvind Kolås <pippin gimp org>
Date:   Tue Nov 21 14:02:44 2017 +0100

    ppm-load: fix file type registration by remove trailing colon
    
    as spotted in bug #790656 by massimo

 operations/external/ppm-load.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/operations/external/ppm-load.c b/operations/external/ppm-load.c
index 503272e..146568e 100644
--- a/operations/external/ppm-load.c
+++ b/operations/external/ppm-load.c
@@ -390,7 +390,7 @@ gegl_op_class_init (GeglOpClass *klass)
     ".ppm", "gegl:ppm-load");
 
   gegl_operation_handlers_register_loader (
-    "image/x-portable-graymap:", "gegl:ppm-load");
+    "image/x-portable-graymap", "gegl:ppm-load");
   gegl_operation_handlers_register_loader (
     ".pgm", "gegl:ppm-load");