bitbucket: remove separate OAuth prompt/dialog

Remove the separate "OAuth Required" UI prompt in favour of just always
showing the "Credentials" prompt, where users can select the OAuth auth
mode directly anyway.

Author: mjcheetham

src/shared/Atlassian.Bitbucket.Tests/BitbucketAuthenticationTest.cs

@@ -108,21 +108,6 @@ public async Task BitbucketAuthentication_GetCredentialsAsync_All_NoDesktopSessi
             Assert.Equal(password, result.Credential.Password);
         }
 
-        [Fact]
-        public async Task BitbucketAuthentication_ShowOAuthRequiredPromptAsync_SucceedsAfterUserInput()
-        {
-            var context = new TestCommandContext();
-            context.Terminal.Prompts["Press enter to continue..."] = " ";
-
-            var bitbucketAuthentication = new BitbucketAuthentication(context);
-
-            var result = await bitbucketAuthentication.ShowOAuthRequiredPromptAsync();
-
-            Assert.True(result);
-            Assert.Equal($"Your account has two-factor authentication enabled.{Environment.NewLine}" +
-                                           $"To continue you must complete authentication in your web browser.{Environment.NewLine}", context.Terminal.Messages[0].Item1);
-        }
-
         [Fact]
         public async Task BitbucketAuthentication_GetCredentialsAsync_AllModes_NoUser_BBCloud_HelperCmdLine()
         {