Bump bazel vesion to 6.2.0

Also demote severity level for bug pattern: PreferredInterfaceType, aka
MutableConstantField: [1] from error to warning.

Also fix DoubleBraceInitialization error prone bug pattern [2].

[1] https://errorprone.info/bugpattern/PreferredInterfaceType
[2] https://errorprone.info/bugpattern/DoubleBraceInitialization

Change-Id: I04b7d0792e67cbc51e3939bd47c2ea13a685cf0d
diff --git a/.bazelversion b/.bazelversion
index 0062ac9..6abaeb2 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-5.0.0
+6.2.0
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/ArchiveCommandTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/ArchiveCommandTest.java
index f2cceac..411eab3 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/ArchiveCommandTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/api/ArchiveCommandTest.java
@@ -261,14 +261,10 @@
 			File archive = new File(getTemporaryDirectory(),
 					"archive." + format);
 
-			archive(git, archive, fmt, new HashMap<String, Object>() {{
-				put("compression-level", 1);
-			}});
+			archive(git, archive, fmt, Map.of("compression-level", 1));
 			int sizeCompression1 = getNumBytes(archive);
 
-			archive(git, archive, fmt, new HashMap<String, Object>() {{
-				put("compression-level", 9);
-			}});
+			archive(git, archive, fmt, Map.of("compression-level", 9));
 			int sizeCompression9 = getNumBytes(archive);
 
 			assertTrue(sizeCompression1 > sizeCompression9);
diff --git a/tools/BUILD b/tools/BUILD
index 1e67108..dd081d9 100644
--- a/tools/BUILD
+++ b/tools/BUILD
@@ -68,7 +68,7 @@
         "-Xep:LiteralClassName:ERROR",
         "-Xep:MissingFail:ERROR",
         "-Xep:MissingOverride:ERROR",
-        "-Xep:MutableConstantField:ERROR",
+        "-Xep:MutableConstantField:WARN",
         "-Xep:NarrowingCompoundAssignment:ERROR",
         "-Xep:NonAtomicVolatileUpdate:ERROR",
         "-Xep:NonOverridingEquals:ERROR",