Remove BaseAzureDevOpsPullRequestSettings.SourceBranch (#457)

Author: pascalberger

src/Cake.AzureDevOps/Repos/PullRequest/BaseAzureDevOpsPullRequestSettings.cs

@@ -81,12 +81,6 @@ protected BaseAzureDevOpsPullRequestSettings(IAzureDevOpsCredentials credentials
         /// </summary>
         public Uri RepositoryUrl { get; }
 
-        /// <summary>
-        /// Gets the branch for which the pull request is made.
-        /// </summary>
-        [Obsolete("Use SourceRefName instead.")]
-        public string SourceBranch => this.SourceRefName;
-
         /// <summary>
         /// Gets the branch for which the pull request is made.
         /// </summary>