[clang][OpenMP] Fix typo in comment, NFC

Author: kparzysz

clang/include/clang/AST/OpenMPClause.h

@@ -191,7 +191,7 @@ class OMPOneStmtClause : public Base {
 };
 
 /// Class that handles pre-initialization statement for some clauses, like
-/// 'shedule', 'firstprivate' etc.
+/// 'schedule', 'firstprivate' etc.
 class OMPClauseWithPreInit {
   friend class OMPClauseReader;