Fixed new linter warnings

src/compiler/sys.ts

@@ -139,10 +139,6 @@ namespace ts {
                 }
             }
 
-            function getCanonicalPath(path: string): string {
-                return path.toLowerCase();
-            }
-
             function getNames(collection: any): string[] {
                 const result: string[] = [];
                 for (let e = new Enumerator(collection); !e.atEnd(); e.moveNext()) {
@@ -357,10 +353,6 @@ namespace ts {
                 }
             }
 
-            function getCanonicalPath(path: string): string {
-                return useCaseSensitiveFileNames ? path.toLowerCase() : path;
-            }
-
             function getAccessibleFileSystemEntries(path: string): FileSystemEntries {
                 try {
                     const entries = _fs.readdirSync(path || ".").sort();
@@ -501,4 +493,4 @@ namespace ts {
             return undefined; // Unsupported host
         }
     })();
-}
+}