Update RSpec raise_error to be more specific

[shortdudey123]

Fixes the following warning

WARNING: Using the `raise_error` matcher without providing a specific error or message risks false positives, since `raise_error` will match when Ruby raises a `NoMethodError`, `NameError` or `ArgumentError`, potentially allowing the expectation to pass without even executing the method you are intending to call. Actual error raised was #<YamlLint::FileNotFoundError: /does/not/exist: no such file>. Instead consider providing a specific error class or message. This message can be suppressed by setting: `RSpec::Expectations.configuration.on_potential_false_positives = :nothing`. Called from /Users/username/github/yamllint/spec/linter_spec.rb:12:in `block (2 levels) in <top (required)>'.