patch 9.0.0267: Coverity workflow still uses Ubuntu 18.04

Problem:    Coverity workflow still uses Ubuntu 18.04.
Solution:   Use Ubuntu 20.04

.github/workflows/coverity.yml

@@ -6,7 +6,7 @@ on:
 
 jobs:
   scan:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-20.04
 
     env:
       CC: gcc

src/version.c

@@ -727,6 +727,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    267,
 /**/
     266,
 /**/