[ruby/syntax_suggest] Use hard-coded filename for executables.

It's hard to handle between ruby/syntax_suggest and ruby/ruby at gemspec.

https://github.com/ruby/syntax_suggest/commit/0ee7496668

lib/syntax_suggest/syntax_suggest.gemspec

@@ -27,6 +27,6 @@ Gem::Specification.new do |spec|
     `git ls-files -z`.split("\x0").reject { |f| f.match(%r{^(test|spec|features|assets)/}) }
   end
   spec.bindir = "exe"
-  spec.executables = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
+  spec.executables = ["syntax_suggest"]
   spec.require_paths = ["lib"]
 end