Fix warnings.

Author: uhafner

src/main/java/io/jenkins/plugins/forensics/blame/FileBlame.java

@@ -47,6 +47,8 @@ private FileBlame(final TreeString fileName) {
      *
      * @return this
      */
+    @Serial
+    @SuppressWarnings("DataFlowIssue")
     private Object readResolve() {
         if (timeByLine == null) {
             timeByLine = new HashMap<>();

src/main/java/io/jenkins/plugins/forensics/miner/FileStatistics.java

@@ -63,6 +63,7 @@ public String getFileName() {
      *
      * @return this
      */
+    @Serial
     @SuppressWarnings("deprecation")
     @SuppressFBWarnings(value = "RCN_REDUNDANT_NULLCHECK_OF_NONNULL_VALUE", justification = "Deserialization of instances that do not have all fields yet")
     private Object readResolve() {

src/main/java/io/jenkins/plugins/forensics/reference/ReferenceRecorder.java

@@ -182,7 +182,6 @@ private Optional<ReferenceBuild> searchForReferenceBuildWithRequiredStatus(final
         var job = run.getParent();
         var topLevel = job.getParent();
         if (topLevel instanceof MultiBranchProject multiBranchProject) {
-
             logger.logInfo("Found a `MultiBranchProject`, trying to resolve the target branch from the configuration");
 
             var targetBranch = getTargetBranch();