[clang][utils] Minor tweak to make-ast-dump-check.sh

Remove the space after the "CHECK:" on each line. This space makes the use
of FileCheck --match-full-lines impossible.

clang/utils/make-ast-dump-check.sh

@@ -74,11 +74,11 @@ BEGIN {
 }
 
 matched_last_line == 0 {
-  print "// ${prefix}: " s
+  print "// ${prefix}:" s
 }
 
 matched_last_line == 1 {
-  print "// ${prefix}-NEXT: " s
+  print "// ${prefix}-NEXT:" s
 }
 
 {