Fix forbiddenapis violation: use explicit UTF-8 charset

Replace new String(byte[]) with new String(byte[], StandardCharsets.UTF_8)
to satisfy the forbiddenapis Maven plugin check.

Author: guizmaii

modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/fetch/TypeScriptFetchClientCodegenTest.java

@@ -21,6 +21,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -469,7 +470,7 @@ public void testRequestOptsInInterfaceByDefault() throws IOException {
         TestUtils.assertFileExists(apiFile);
 
         // Read file content and split into interface and class sections
-        String content = new String(Files.readAllBytes(apiFile));
+        String content = new String(Files.readAllBytes(apiFile), StandardCharsets.UTF_8);
         int interfaceStart = content.indexOf("export interface PetControllerApiInterface");
         int classStart = content.indexOf("export class PetControllerApi");
         String interfaceSection = content.substring(interfaceStart, classStart);
@@ -494,7 +495,7 @@ public void testRequestOptsNotInInterfaceWhenDisabled() throws IOException {
         TestUtils.assertFileExists(apiFile);
 
         // Read file content and split into interface and class sections
-        String content = new String(Files.readAllBytes(apiFile));
+        String content = new String(Files.readAllBytes(apiFile), StandardCharsets.UTF_8);
         int interfaceStart = content.indexOf("export interface PetControllerApiInterface");
         int classStart = content.indexOf("export class PetControllerApi");
         String interfaceSection = content.substring(interfaceStart, classStart);