fix(run): fix quotes error in osascript notification

Resolve a quoting error in the "run completed" notification when using
osascript:

    33:38: syntax error: A identifier can’t go after this “"”. (-2740)

credits: @jcfranco for OSX testing assistance

gh-fzf

@@ -658,7 +658,7 @@ notify_run_completed() {
     IFS=$OLDIFS
 
     title="${workflow:-GitHub Action run completed}"
-    body="${conclusion}${branch:+ on \"$branch\" branch}"
+    body="${conclusion}${branch:+" on '$branch' branch"}"
 
     if has dunstify; then
         [ -n "$urgency" ] &&