Fix hour-dependent spec in error_tracking_shared_context.rb

The test was failing because the expected format included a leading 0 in 08:01:29 AM UTC instead of omitting it in 8:01:29 AM UTC. As https://ruby-doc.org/stdlib-2.6.5/libdoc/date/rdoc/DateTime.html#method-i-strftime mentions, we can omit the leading value by using %-l in strftime.