Fix tests failing with rspec 3.12

[traylenator]

Patch from

• https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1027092
• https://salsa.debian.org/ruby-team/ruby-stomp/-/commit/5be6383a7a34a1d1891708d6aa8688cb4a6f89a5

resolves rspec failure:

$ rspec --fail-fast spec/client_spec.rb
RSpec version: 3.8.0
Traceback (most recent call last):
	9: from /home/straylen/pkgs/rubygem-stomp/stomp-1.4.9/lib/client/utils.rb:194:in `block in start_listeners'
	8: from /home/straylen/pkgs/rubygem-stomp/stomp-1.4.9/lib/client/utils.rb:194:in `loop'
	7: from /home/straylen/pkgs/rubygem-stomp/stomp-1.4.9/lib/client/utils.rb:195:in `block (2 levels) in start_listeners'
	6: from /usr/share/gems/gems/rspec-mocks-3.8.1/lib/rspec/mocks/test_double.rb:102:in `method_missing'
	5: from /usr/share/gems/gems/rspec-mocks-3.8.1/lib/rspec/mocks/proxy.rb:202:in `raise_unexpected_message_error'
	4: from /usr/share/gems/gems/rspec-mocks-3.8.1/lib/rspec/mocks/error_generator.rb:50:in `raise_unexpected_message_error'
	3: from /usr/share/gems/gems/rspec-mocks-3.8.1/lib/rspec/mocks/error_generator.rb:311:in `__raise'
	2: from /usr/share/gems/gems/rspec-mocks-3.8.1/lib/rspec/mocks/error_generator.rb:327:in `notify'
	1: from /usr/share/gems/gems/rspec-support-3.8.2/lib/rspec/support.rb:106:in `notify_failure'
/usr/share/gems/gems/rspec-support-3.8.2/lib/rspec/support.rb:97:in `block in <module:Support>': #<Double "connection"> received unexpected message :receive with (no args) (RSpec::Mocks::MockExpectationError)
.#<Thread:0x000055a54150bd60@/home/straylen/pkgs/rubygem-stomp/stomp-1.4.9/lib/client/utils.rb:193 run> terminated with exception (report_on_exception is true):
Traceback (most recent call last):
	6: from /home/straylen/pkgs/rubygem-stomp/stomp-1.4.9/lib/client/utils.rb:194:in `block in start_listeners'
	5: from /home/straylen/pkgs/rubygem-stomp/stomp-1.4.9/lib/client/utils.rb:194:in `loop'

Fixes: #164