add deprecation message to rspec command

ruby/README.md

@@ -51,7 +51,9 @@ The runner also comes with a tool to investigate leaky tests:
 minitest-queue --queue path/to/test_order.log --failing-test 'SomeTest#test_something' bisect -Itest test/**/*_test.rb
 ```
 
-### RSpec
+### RSpec [DEPRECATED]
+
+> ⛔️ The rspec-queue runner is DEPRECATED, so we can focus on the minitest-queue runner exclusively and improve it more.
 
 Assuming you use one of the supported CI providers, the command can be as simple as:
 
@@ -67,4 +69,4 @@ rspec-queue --queue redis://example.com --timeout 600 --report
 
 #### Limitations
 
-Because of how `ci-queue` execute the examples, `before(:all)` and `after(:all)` hooks are not supported. `rspec-queue` will explicitly reject them.
+Because of how `ci-queue` execute the examples, `before(:all)` and `after(:all)` hooks are not supported. `rspec-queue` will explicitly reject them.