[gtksourceview] rst.lang: Fix field regexp

[Christian Hergert <chergert src gnome org>]

commit 0c8157a8fb6ab7fb2150bcc70d3c2b1ccdfd453a
Author: Pierre Ossman <ossman cendio se>
Date:   Fri Oct 15 15:49:42 2021 +0200

    rst.lang: Fix field regexp
    
    Use the same regexp as the official parser to make sure we grab the same
    things.

 data/language-specs/rst.lang | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/data/language-specs/rst.lang b/data/language-specs/rst.lang
index dac1b8d2..6a57449a 100644
--- a/data/language-specs/rst.lang
+++ b/data/language-specs/rst.lang
@@ -99,7 +99,7 @@
     </context>
 
     <context id="field" style-ref="bullet">
-      <match>^\s*:.+?:</match>
+      <match>:(?![: ])([^:\\]|\\.|:(?!([ `]|$)))*(?&lt;! ):( +|$)</match>
     </context>
 
     <define-regex id="legal-start" extended="true">