[flang] Fix a warning

This patch fixes:

  flang/include/flang/Semantics/openmp-modifiers.h:45:69: error: extra
  ';' outside of a function is incompatible with C++98
  [-Werror,-Wc++98-compat-extra-semi]

Author: kazutakahirata

flang/include/flang/Semantics/openmp-modifiers.h

@@ -42,7 +42,7 @@ namespace Fortran::semantics {
 // or post-modifier (i.e. item: modifier). The default is pre-.
 // Add an additional property that reflects the type of modifier.
 
-ENUM_CLASS(OmpProperty, Required, Unique, Exclusive, Ultimate, Post);
+ENUM_CLASS(OmpProperty, Required, Unique, Exclusive, Ultimate, Post)
 using OmpProperties = common::EnumSet<OmpProperty, OmpProperty_enumSize>;
 using OmpClauses =
     common::EnumSet<llvm::omp::Clause, llvm::omp::Clause_enumSize>;