[gnome-shell] st: Remove invalid introspection annotation

[Florian Müllner <fmuellner src gnome org>]

commit 923d92634504e461c3207c0e6a558d3ab43d6ad9
Author: Florian Müllner <fmuellner gnome org>
Date:   Fri Aug 14 00:04:38 2020 +0200

    st: Remove invalid introspection annotation
    
    (optional) is only valid for (out) or (inout) parameters (that are
    marked as such).
    
    However GError** arguments appear as throws="1" in the GIR anyway
    instead of an explicit parameter, so we don't need any annotation
    at all here.
    
    https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1408

 src/st/st-theme.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/st/st-theme.c b/src/st/st-theme.c
index e9716fe631..d1bde3fc02 100644
--- a/src/st/st-theme.c
+++ b/src/st/st-theme.c
@@ -254,7 +254,7 @@ insert_stylesheet (StTheme      *theme,
  * st_theme_load_stylesheet:
  * @theme: a #StTheme
  * @file: a #GFile
- * @error: (optional): a #GError
+ * @error: a #GError
  *
  * Load the stylesheet associated with @file.
  *