Change regular expression for git blame to one more supported

Change regular expression in git blame, removing braces. New expression is supported on various awk engines used in some distributions as default ones. As trade-off, the new expression accepts more input character sequences.

rc/tools/git.kak

@@ -76,7 +76,7 @@ Available commands:\n  add\n  rm\n  blame\n  commit\n  checkout\n  diff\n  hide-
                       print "set-option -add buffer=" ENVIRON["kak_bufname"] " git_blame_flags " flag | cmd
                       close(cmd)
                   }
-                  /^([0-9a-f]{40}) ([0-9]+) ([0-9]+) ([0-9]+)/ {
+                  /^([0-9a-f]+) ([0-9]+) ([0-9]+) ([0-9]+)/ {
                       send_flags()
                       sha=$1
                       line=$3