Fixes for safe_level, trim_mode argument of ERB.new is deprecated warning

[piyushawasthi]

/workspaces/warbler/lib/warbler/jar.rb:288: warning: Passing safe_level with the 2nd argument of ERB.new is deprecated. Do not use it, and specify other arguments as keyword arguments. /workspaces/warbler/lib/warbler/jar.rb:288: warning: Passing trim_mode with the 3rd argument of ERB.new is deprecated. Use keyword argument like ERB.new(str, trim_mode: ...) instead.

[olleolleolle]

So, we are running many versions of Ruby (as JRuby versions), and we probably need to support more argument lists than the new one.

I suggest adding a conditional, checking that the keyword argument way of doing things is available.

[doconnor-clintel]

May be worth as a separate PR dropping some of the older jruby versions as unsupported from CI.

[chadlwilson]

This was subsequently fixed in #559 so can be closed.