Bump rbs from v3.6.0 to v3.7.0 and steep from v1.8.0 to v1.8.1

[ydah]

The following warnings and errors have been fixed as a result of the version update:

bundle exec steep check
# Type checking files:

............F.........................F..................................F...FF.......F......

lib/lrama/grammar/parameterizing_rule/rhs.rb:19:23: [warning] Empty hash doesn't have type annotation
│ Diagnostic ID: Ruby::UnannotatedEmptyCollection
│
└           var_to_arg = {}
                         ~~

lib/lrama/bitmap.rb:16:10: [warning] Empty array doesn't have type annotation
│ Diagnostic ID: Ruby::UnannotatedEmptyCollection
│
└       a = []
            ~~

lib/lrama/grammar/rule_builder.rb:70:28: [warning] Empty array doesn't have type annotation
│ Diagnostic ID: Ruby::UnannotatedEmptyCollection
│
└         resolved_builders = []
                              ~~

lib/lrama/lexer/token/user_code.rb:19:23: [warning] Empty array doesn't have type annotation
│ Diagnostic ID: Ruby::UnannotatedEmptyCollection
│
└           references = []
                         ~~

lib/lrama/state/reduce.rb:30:36: [error] Type annotation has a syntax error: Failed to parse a type in annotation
│ Diagnostic ID: Ruby::AnnotationSyntaxError
│
└           # @type ivar @look_ahead: Array<Grammar::Symbol>
                                      ~~~~~~~~~~~~~~~~~~~~~~

lib/lrama/grammar.rb:385:15: [warning] Empty array doesn't have type annotation
│ Diagnostic ID: Ruby::UnannotatedEmptyCollection
│
└       errors = []
                 ~~

Detected 6 problems from 6 files
rake aborted!