make it compatible with ESLint <v8

Author: Thomasan1999

Diff for: lib/rules/prefer-use-template-ref.js

@@ -56,7 +56,7 @@ function createIndent(node) {
  *  @param fixer {RuleFixer}
  * */
 function addUseTemplateRefImport(context, fixer) {
-  const sourceCode = context.sourceCode
+  const sourceCode = context.getSourceCode()
 
   if (!sourceCode) {
     return