Enable RuboCop Style/RedundantReturn

[kpumuk]

Enable Style/RedundantReturn and remove explicit return keywords where Ruby already returns the final expression.

The Ruby generator now emits service client receive calls as final expressions. Generated void and oneway paths that previously used a bare early return emit nil instead, preserving their control flow and return value while keeping generated code compliant with the cop. Functional coverage verifies the generated non-void client method shape.

This follows the merged Style/RedundantBegin PR #3727; its diff contains only the RedundantReturn layer.

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[Copilot]

Pull request overview

Enables RuboCop Style/RedundantReturn for the Ruby codebase and updates Ruby sources plus the Ruby code generator output to avoid explicit return where Ruby already returns the final expression, while keeping generated client/process control flow and return values consistent.

Changes:

• Enable Style/RedundantReturn in lib/rb/.rubocop.yml.
• Remove redundant trailing return statements across Ruby tutorial/test/runtime code where the final expression is sufficient.
• Update the Ruby generator to emit recv_* calls as final expressions and adjust generated void/oneway terminal return sites to nil, with a functional test asserting the generated non-void client method shape.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tutorial/rb/RubyServer.rb	Removes redundant returns in tutorial handler methods.
test/rb/integration/TestServer.rb	Removes redundant returns in Ruby integration test handler methods.
lib/rb/lib/thrift/transport/memory_buffer_transport.rb	Removes redundant return true in open?.
lib/rb/lib/thrift/transport/framed_transport.rb	Removes redundant returns in read_byte and factory get_transport.
lib/rb/lib/thrift/transport/buffered_transport.rb	Removes redundant returns in open?, read_byte, and factory get_transport.
lib/rb/lib/thrift/transport/base_transport.rb	Removes redundant return in read_byte and factory get_transport.
lib/rb/lib/thrift/protocol/json_protocol.rb	Removes redundant trailing returns (and case-branch returns) where the expression value suffices.
lib/rb/lib/thrift/protocol/binary_protocol.rb	Removes redundant return in protocol factory get_protocol.
lib/rb/.rubocop.yml	Enables Style/RedundantReturn.
compiler/cpp/tests/rb/t_rb_generator_functional_tests.cc	Adds an assertion for generated non-void client method shape (send_* followed by recv_* as final expression).
compiler/cpp/src/thrift/generate/t_rb_generator.cc	Updates Ruby generator output to avoid redundant returns and emit nil for terminal void/oneway paths.

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