CS-18599: csdx content-type:diagram cmd fix

Added api_key to headers for getContentTypes function tp resolve below command issue
csdx content-type:diagram
csdx content-type:list

Author: Ashish-SA-CS

src/core/contentstack/client.ts

@@ -113,10 +113,12 @@ export default class ContentstackClient {
     try {
       const response = await this.instance.get('/content_types', {
         params: {
-          api_key: api_key,
           include_count: true,
           include_global_field_schema: includeGlobalFields,
         },
+        headers: {
+          api_key,
+        },
       })
 
       return response.data