Change protected visibility to private

Not needed, and not recommended per https://docs.ruby-lang.org/en/3.3/Module.html#method-i-protected

README.md

@@ -18,7 +18,7 @@ class CreateUser < SorbetOperation::Base
     @user_params = user_params
   end
 
-  protected
+  private
 
   sig { returns(ValueType) }
   def execute
@@ -71,7 +71,7 @@ An operation is a Ruby class that derives from `SorbetOperation::Base`. `SorbetO
 1. define the return type using the `ValueType` generic type member
 2. define an `#execute` method that returns a `ValueType`
 
-The `#execute` method should be `protected` or `private`, since it is not meant to be invoked directly; rather, operation callers should use the `#perform` public method to actually perform the operation. (Unfortunately, at this time there is no mechanism to enforce that `#execute` is not a public method on child classes, so it's up to the programmer to be vigilant.)
+The `#execute` method should be `private`, since it is not meant to be invoked directly; rather, operation callers should use the `#perform` public method to actually perform the operation. (Unfortunately, at this time there is no mechanism to enforce that `#execute` is not a public method on child classes, so it's up to the programmer to be vigilant.)
 
 The `#execute` method does not take any arguments. Most operations require one or more input values. Input values should be passed to the `#initialize` constructor method and stored as instance variables, which can then be accessed from the `#execute` body.
 

lib/sorbet_operation/base.rb

@@ -57,7 +57,7 @@ def perform
     sig { params(logger: ::Logger).void }
     attr_writer :logger
 
-    protected
+    private
 
     # Implement this method in subclasses to perform the operation.
     #
@@ -70,7 +70,7 @@ def perform
     # exception. The exception will not be caught and will be propagated to
     # the caller.
     #
-    # This method should be declared as `protected` in subclasses to prevent
+    # This method should be declared as `private` in subclasses to prevent
     # callers from calling it directly. Callers should instead call {#perform}
     # to perform the operation and get the result.
     sig { abstract.returns(ValueType) }

test/sorbet_operation/base_test.rb

@@ -19,7 +19,7 @@ def initialize(dividend, divisor)
       @divisor = divisor
     end
 
-    protected
+    private
 
     sig { override.returns(Float) }
     def execute