Fix expecting content-type headers

It does not contain the charset anymore, for an unknown reason. It's not a
big deal though, so just fix it.

Change-Id: I0583a8cedfecb9353d23978269f8a6f1fee171a4

aodh/tests/functional/gabbi/gabbits/alarms.yaml

@@ -43,7 +43,7 @@ tests:
   status: 201
   response_headers:
       location: /$SCHEME://$NETLOC/v2/alarms/
-      content-type: application/json; charset=UTF-8
+      content-type: application/json
   response_json_paths:
       $.severity: low
       $.threshold_rule.threshold: 300.0
@@ -59,7 +59,7 @@ tests:
       $.threshold_rule.threshold: 300.0
       $.threshold_rule.comparison_operator: eq
   response_headers:
-      content-type: application/json; charset=UTF-8
+      content-type: application/json
 
 - name: updateAlarm
   desc: Updates a specified alarm.
@@ -112,7 +112,7 @@ tests:
   url: /v2/alarms/$RESPONSE['$[0].alarm_id']/state
   method: GET
   response_headers:
-      content-type: application/json; charset=UTF-8
+      content-type: application/json
   response_json_paths:
       $: alarm
 

aodh/tests/functional/gabbi/gabbits/basic.yaml

@@ -10,7 +10,7 @@ tests:
 -    name: quick root check
      url: /
      response_headers:
-         content-type: application/json; charset=UTF-8
+         content-type: application/json
      response_strings:
          - '"base": "application/json"'
      response_json_paths: