Remove timezone field from time_array in spec

Specifying a timezone in Time#utc in jruby-9.3.4.0 raises a
`no implicit conversion of String into Integer` error.
AFAICT, this timezone serves no purpose in the running of the test, so this
commit removes it

Author: robbavey

spec/bson/logstash_timestamp_spec.rb

@@ -2,7 +2,7 @@
 require_relative "../spec_helper"
 
 describe ::LogStash::Timestamp do
-  let(:time_array) { [1918,11,11,11,0,0, "+00:00"] }
+  let(:time_array) { [1918,11,11,11,0,0] }
   let(:a_time) { Time.utc(*time_array) }
   let(:bson_time) { Time.utc(*time_array).to_bson }