fix lint errors

Author: vladima

src/compiler/checker.ts

@@ -1028,7 +1028,7 @@ namespace ts {
 
             // Module names are escaped in our symbol table.  However, string literal values aren't.
             // Escape the name in the "require(...)" clause to ensure we find the right symbol.
-            let moduleName = escapeIdentifier(moduleReferenceLiteral.text);
+            const moduleName = escapeIdentifier(moduleReferenceLiteral.text);
 
             if (moduleName === undefined) {
                 return;