Remove unnecessary size checks from XChaCha20

libsodium handles the case of both a long and short key gracefully

lib/paseto/sodium/stream/base.rb

@@ -33,15 +33,9 @@ def self.key_bytes
         # Create a new Stream.
         #
         # Sets up Stream with a secret key for encrypting and decrypting messages.
-        #
-        # @param key [String] The key to encrypt and decrypt with
-        #
-        # @raise [RbNaCl::LengthError] on invalid keys
-        #
-        # @return [RbNaCL::Stream::Base] The new Stream construct, ready to use
         sig { params(key: String).void }
         def initialize(key)
-          @key = T.let(RbNaCl::Util.check_string(key, key_bytes, 'Secret key'), String)
+          @key = key
         end
 
         sig { params(nonce: String, message: T.nilable(String)).returns(String) }

spec/paseto/sodium/stream/x_cha_cha20_xor_spec.rb

@@ -42,14 +42,6 @@
     it 'raises on a nil key' do
       expect { described_class.new(nil) }.to raise_error(TypeError)
     end
-
-    it 'raises on a short key' do
-      expect { described_class.new('hello') }.to raise_error RbNaCl::LengthError
-    end
-
-    it 'raises on a long key' do
-      expect { described_class.new("hello#{key}") }.to raise_error RbNaCl::LengthError
-    end
   end
 
   describe '#encrypt' do