Add chartset=utf-8 to UAA axios password request

In axios release v0.21.2 they have [removed the charset field from application/json Content-type header](axios/axios#2154) which UAA api doesn't like so paas-admin password reset requests have been 404ing for users.

This adds the charset back so all is good now.

src/lib/uaa/uaa.test.ts

@@ -283,7 +283,7 @@ describe('lib/uaa test suite', () => {
         const acceptHeader = this.req.headers['accept'];
         const contentTypeHeader = this.req.headers['content-type'];
 
-        if (acceptHeader !== 'application/json' || contentTypeHeader !== 'application/json') {
+        if (acceptHeader !== 'application/json' || contentTypeHeader !== 'application/json;chartset=utf-8') {
           return [
             404,
             {

src/lib/uaa/uaa.ts

@@ -305,7 +305,7 @@ export default class UAAClient {
       data: username,
       headers: {
         'Accept': 'application/json',
-        'Content-Type': 'application/json',
+        'Content-Type': 'application/json;chartset=utf-8',
       },
     });