[gimp] app: s/plug-In/plug-in in a GUI-visible string.

[Jehan <jehanp src gnome org>]

commit a6aa14bca28a96b9558d01150f1172bc7e26bf12
Author: Jehan <jehan girinstud io>
Date:   Mon Feb 11 15:17:36 2019 +0100

    app: s/plug-In/plug-in in a GUI-visible string.

 app/file/file-open.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/app/file/file-open.c b/app/file/file-open.c
index 4550725c46..0747c7cf4a 100644
--- a/app/file/file-open.c
+++ b/app/file/file-open.c
@@ -265,7 +265,7 @@ file_open_image (Gimp                *gimp,
     {
       if (error && ! *error)
         g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
-                     _("%s plug-In could not open image"),
+                     _("%s plug-in could not open image"),
                      gimp_procedure_get_label (GIMP_PROCEDURE (file_proc)));
     }