[flang][test] Recognize !$acc and !$omp spelled with capital letters (#118666)

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

---------

Co-authored-by: Michael Kruse <[email protected]>

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:|\$omp|\$acc).*", "", line, re.I)
         text = re.sub(r"^\s*$", "", text)
         diff1 += text