workflows/ci.yml fix push branch regex (#1445)

The current pattern matches the following:
"sdf", "sdf0", "sdf1", ..., "sdf8", "sdf9"
of which "sdf" is incorrect, and only "sdf9"
is currently supported. This updates the pattern
to match single digits "sdf1" - "sdf9" and double
digits "sdf10" to "sdf99".

Signed-off-by: Steve Peters <scpeters@openrobotics.org>

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on:
   pull_request:
   push:
     branches:
-      - 'sdf[0-9]?'
+      - 'sdf[1-9]?[0-9]'
       - 'main'
 
 jobs: