Update docs for Definition request

[andyw8]

Support for classes and modules was added in #878

[github-actions]

Benchmark results in seconds (slowest at top)
textDocument/completion average: 0.261372 std_dev: 0.005076
textDocument/diagnostic average: 0.039949 std_dev: 0.010041
textDocument/definition average: 0.005465 std_dev: 0.003186
textDocument/selectionRange average: 0.004055 std_dev: 0.000421
textDocument/documentHighlight average: 0.002466 std_dev: 0.000141
textDocument/codeLens average: 0.002451 std_dev: 0.00017
textDocument/documentLink average: 0.002437 std_dev: 0.000206
textDocument/documentSymbol average: 0.002405 std_dev: 9.2e-05
textDocument/semanticTokens/full average: 0.002394 std_dev: 0.000268
textDocument/foldingRange average: 0.00223 std_dev: 0.0002
textDocument/semanticTokens/range average: 0.00159 std_dev: 0.00012
textDocument/inlayHint average: 0.001359 std_dev: 0.000124
codeAction/resolve average: 0.001351 std_dev: 0.000122
textDocument/hover average: 0.001321 std_dev: 9.3e-05
textDocument/onTypeFormatting average: 0.000809 std_dev: 9.1e-05
textDocument/formatting average: 0.000808 std_dev: 0.000294
textDocument/codeAction average: 0.00079 std_dev: 8.1e-05
================================================================================
Comparison with main branch:
textDocument/semanticTokens/full unchanged
textDocument/semanticTokens/range unchanged
textDocument/documentSymbol faster by 4.58 %
textDocument/foldingRange unchanged
textDocument/formatting unchanged
textDocument/diagnostic unchanged
textDocument/documentLink unchanged
textDocument/inlayHint unchanged
textDocument/selectionRange unchanged
textDocument/documentHighlight unchanged
textDocument/hover unchanged
textDocument/codeAction unchanged
textDocument/onTypeFormatting unchanged
codeAction/resolve unchanged
textDocument/completion faster by 2.389 %
textDocument/codeLens unchanged
textDocument/definition unchanged
================================================================================
Missing benchmarks:
RubyLsp::Requests::ShowSyntaxTree