Remove CanOnlyWriteStringError, due to it being private API

lib/dry/files/error.rb

@@ -116,21 +116,5 @@ def initialize(path)
         super("not a memory file `#{path}'")
       end
     end
-
-    # Internal file system adapters can only take
-    # strings as arguments to their `write` methods.
-    # (The public API can take string or array of strings)
-    #
-    # @since x.x.x
-    # @api private
-    class CanOnlyWriteStringError < Error
-      # Instantiate a new error
-      #
-      # @since x.x.x
-      # @api private
-      def initialize
-        super("Can only write a String (use `join` or `to_s`)")
-      end
-    end
   end
 end

lib/dry/files/file_system.rb

@@ -129,13 +129,10 @@ def touch(path, **kwargs)
       # @param content [String] the content to write
       #
       # @raise [Dry::Files::IOError] in case of I/O error
-      # @raise [CanOnlyWriteStringError] if content param isn't a String
       #
       # @since 0.1.0
       # @api private
       def write(path, content)
-        raise CanOnlyWriteStringError unless content.is_a?(String)
-
         mkdir_p(path)
 
         self.open(path, WRITE_MODE) do |f|

spec/unit/dry/files/file_system_spec.rb

@@ -217,14 +217,6 @@
         path.chmod(mode)
       end
     end
-
-    it "raises error when trying to write non-string" do
-      path = root.join("write")
-      expect { subject.write(path, %w[new words]) }.to raise_error do |exception|
-        expect(exception).to be_kind_of(Dry::Files::CanOnlyWriteStringError)
-        expect(exception.message).to eq("Can only write a String (use `join` or `to_s`)")
-      end
-    end
   end
 
   describe "#join" do

spec/unit/dry/files/memory_file_system_spec.rb

@@ -188,14 +188,6 @@
         path.chmod(mode)
       end
     end
-
-    it "raises error when trying to write non-string" do
-      path = subject.join("write")
-      expect { subject.write(path, %w[new words]) }.to raise_error do |exception|
-        expect(exception).to be_kind_of(Dry::Files::CanOnlyWriteStringError)
-        expect(exception.message).to eq("Can only write a String (use `join` or `to_s`)")
-      end
-    end
   end
 
   describe "#join" do