[typescript-fetch] Use typed comparion

Co-authored-by: Esteban Gehring <[email protected]>

Author: manuel-covas

modules/openapi-generator/src/main/resources/typescript-fetch/modelEnum.mustache

@@ -3,7 +3,7 @@
 export function instanceOf{{classname}}(value: any): boolean {
     for (const key in {{classname}}) {
         if (Object.prototype.hasOwnProperty.call({{classname}}, key)) {
-            if ({{classname}}[key] == value) {
+            if ({{classname}}[key] === value) {
                 return true;
             }
         }