github: return PAT token from view model

Fix a bug in the in-proc UI logic for returning the personal access
token. We were accidentally returning the password field rather than the
token field for PATs.

src/shared/GitHub/GitHubAuthentication.cs

@@ -144,7 +144,7 @@ public async Task<AuthenticationPromptResult> GetAuthenticationAsync(Uri targetU
                 case AuthenticationModes.Pat:
                     return new AuthenticationPromptResult(
                         AuthenticationModes.Pat,
-                        new GitCredential(userName, viewModel.Password)
+                        new GitCredential(userName, viewModel.Token)
                     );
 
                 default: