[flang] Add new hints to expected warnings (#146399)

I added a new test with warnings, but warnings are now emitted with
hints. Add them to the new test.

Author: klausler

flang/test/Semantics/bug1046.f90

@@ -1,17 +1,15 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1 -pedantic -Werror
-!WARNING: INTEGER(4) 0**0 is not defined
+!WARNING: INTEGER(4) 0**0 is not defined [-Wfolding-exception]
 print *, 0**0
-!WARNING: REAL/COMPLEX 0**0 is not defined
+!WARNING: REAL/COMPLEX 0**0 is not defined [-Wfolding-exception]
 print *, 0**0.
-!WARNING: invalid argument on power with INTEGER exponent
+!WARNING: invalid argument on power with INTEGER exponent [-Wfolding-exception]
 print *, 0.0**0
-!WARNING: REAL/COMPLEX 0**0 is not defined
+!WARNING: REAL/COMPLEX 0**0 is not defined [-Wfolding-exception]
 print *, 0.0**0.
-!WARNING: invalid argument on power with INTEGER exponent
+!WARNING: invalid argument on power with INTEGER exponent [-Wfolding-exception]
 print *, (0.0, 0.0)**0
-!WARNING: REAL/COMPLEX 0**0 is not defined
+!WARNING: REAL/COMPLEX 0**0 is not defined [-Wfolding-exception]
 print *, (0.0, 0.0)**0.
 print *, (0.0, 0.0)**2.5
 end
-
-