[flang][test] Recognize !$acc and !$omp spelled with capital letters

If there are any continuation lines in the source, they will be printed
using capital letters (at least in case of OpenMP). To avoid having them
stripped out, recognize their spellings using capital letters as well.

Author: kparzysz

flang/test/Semantics/test_symbols.py

@@ -29,7 +29,7 @@
 # Strips out blank lines and all comments except for "!DEF:", "!REF:", "!$acc" and "!$omp"
 with open(src, "r") as text_in:
     for line in text_in:
-        text = re.sub(r"!(?![DR]EF:|\$omp|\$acc).*", "", line)
+        text = re.sub(r"!(?![DR]EF:|\$[Oo][Mm][Pp]|\$[Aa][Cc][Cc]).*", "", line)
         text = re.sub(r"^\s*$", "", text)
         diff1 += text