Remove apparently unnecessary .flush() calls.

public/app/plugins/datasource/prometheus/specs/datasource_specs.ts

@@ -278,10 +278,6 @@ describe('PrometheusDatasource', function() {
       }
     };
 
-    beforeEach(function() {
-      ctx.$httpBackend.flush();
-    });
-
     it('should be min interval when greater than auto interval', function() {
       var query = {
         // 6 hour range
@@ -420,10 +416,6 @@ describe('PrometheusDatasource', function() {
       }
     };
 
-    beforeEach(function() {
-      ctx.$httpBackend.flush();
-    });
-
     it('should be unchanged when auto interval is greater than min interval', function() {
       var query = {
         // 6 hour range