Fix spelling

Author: tblah

flang/lib/Lower/OpenMP/PrivateReductionUtils.cpp

@@ -311,7 +311,7 @@ class PopulateInitAndCleanupRegionsHelper {
   /// Any length parameters which have been fetched for the type
   mlir::SmallVector<mlir::Value> lenParams;
 
-  /// If the source variable being privatized definately can't have non-default
+  /// If the source variable being privatized definitely can't have non-default
   /// lower bounds then we don't need to generate code to read them.
   bool cannotHaveNonDefaultLowerBounds;