Remove unnecessary cast of kwargs

The intent here was to pass in what might be kwargs if the keyword
flag was set, indicating that kwargs were being passed in. This
assumption seems ok so I'm not sure why it doesn't hold. In any
case, the cast here is unnecessary and the IRubyObject form will
return null for non-RubyHashes.

The code that triggered this does deal directly with kwargs, but
as a kwrest, forwarding it through a block:

https://github.com/rails/rails/blob/v7.1.1/activesupport/lib/active_support/testing/time_helpers.rb#L176-L183

This could indicate JRuby failing to pass along a keyword flag
when forwarding kwrest.

The additional changes here are:

* Fall back on non-kwargs behavior if last arg turns out not to be
  a hash.
* Remove a redundant reset of the `callInfo` that governs keyword-
  passing.

Fixes jruby#7982

core/src/main/java/org/jruby/RubyTime.java

@@ -1715,16 +1715,21 @@ private IRubyObject initializeNow(ThreadContext context, IRubyObject zone) {
     public IRubyObject initialize(ThreadContext context, IRubyObject[] args) {
         boolean keywords = hasKeywords(context.resetCallInfo());
         IRubyObject zone = null;
-        context.resetCallInfo();
         IRubyObject nil = context.nil;
 
         int argc = args.length;
         if (keywords) {
-            IRubyObject in = ArgsUtil.extractKeywordArg(context, (RubyHash) args[argc - 1], "in");
-            if (in != null && argc > 7) {
-                throw context.runtime.newArgumentError("timezone argument given as positional and keyword arguments");
+            IRubyObject in = ArgsUtil.extractKeywordArg(context, args[argc - 1], "in");
+            if (in != null) {
+                if (argc > 7) {
+                    throw context.runtime.newArgumentError("timezone argument given as positional and keyword arguments");
+                }
+                zone = in;
+            } else {
+                if (argc > 6) {
+                    zone = args[6];
+                }
             }
-            zone = in;
         } else if (argc > 6) {
             zone = args[6];
         }