Upgrade to SpotBugs 4.2.0

Also fix new violation.  Changelog:

https://github.com/spotbugs/spotbugs/blob/4.4.0/CHANGELOG.md

pom.xml

@@ -246,7 +246,14 @@
       <plugin>
         <groupId>com.github.spotbugs</groupId>
         <artifactId>spotbugs-maven-plugin</artifactId>
-        <version>4.0.5</version>
+        <version>4.2.0</version>
+        <dependencies>
+          <dependency>
+            <groupId>com.github.spotbugs</groupId>
+            <artifactId>spotbugs</artifactId>
+            <version>4.4.0</version>
+          </dependency>
+        </dependencies>
         <configuration>
           <effort>Max</effort>
           <omitVisitors>CrossSiteScripting,DefaultEncodingDetector,FindNullDeref</omitVisitors>

src/main/java/org/gaul/s3proxy/ShardedBlobStore.java

@@ -216,9 +216,9 @@ final class ShardedBlobStore extends ForwardingBlobStore {
                                  String container) {
         Map<String, String> currentSuperblockMeta =
                 blob.getMetadata().getUserMetadata();
-        for (String key : expectedMeta.keySet()) {
-            String current = currentSuperblockMeta.get(key);
-            String expected = expectedMeta.get(key);
+        for (Map.Entry<String, String> entry : expectedMeta.entrySet()) {
+            String current = currentSuperblockMeta.get(entry.getKey());
+            String expected = entry.getValue();
             if (!expected.equalsIgnoreCase(current)) {
                 throw new RuntimeException(String.format(
                         "Superblock block for %s does not match: %s, %s",