go/token: fix a typo in a comment

Fixes golang#75632

Change-Id: I71f891eb837147b6ff818ec4b2133c8c07091931
GitHub-Last-Rev: 3eeeea2
GitHub-Pull-Request: golang#76117
Reviewed-on: https://go-review.googlesource.com/c/go/+/716440
Reviewed-by: t hepudds <[email protected]>
Reviewed-by: Robert Griesemer <[email protected]>
Auto-Submit: t hepudds <[email protected]>
Reviewed-by: Alan Donovan <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>

Author: xyproto

src/go/token/position.go

@@ -511,7 +511,7 @@ func (s *FileSet) AddExistingFiles(files ...*File) {
 	//	}
 	//
 	// because all calls to AddFile must be in increasing order.
-	// AddExistingFilesFiles lets us augment an existing FileSet
+	// AddExistingFiles lets us augment an existing FileSet
 	// sequentially, so long as all sets of files have disjoint ranges.
 	// This approach also does not preserve line directives.