Update tests and docs for accessor methods

Since Ruby 3.1, TracePoint can now handle events for accessor methods.

Author: k-tsj

README.md

@@ -61,23 +61,19 @@ assert do
 end
 ```
 
-* Returned values from accessor methods, method missing, or "super" produce nothing report, e.g:
+* Returned values from method missing, or "super" produce nothing report, e.g:
 
 ```ruby
 class Foo
-  attr_accessor :val
+  def method_missing(*)
+    :foo
+  end
 end
 foo = Foo.new
-foo.val = false
-
-assert do
-  # reported (only the value of "foo" and the literal "true")
-  foo.val == true
-end
 
 assert do
   # won't be reported
-  foo.val
+  foo.foo
 end
 ```
 

test/block_test.rb

@@ -285,21 +285,14 @@ def inspect; '#<Class>'; end
       end
 
       t do
-        older = <<END.chomp
-          @obj.to_i.to_i.to_s
-          |              |
-          |              "0"
-          #<Class>
-END
-        newer = <<END.chomp
+        assert_equal <<END.chomp, assertion_message {
           @obj.to_i.to_i.to_s
           |    |    |    |
           |    |    |    "0"
           |    |    0
           |    0
           #<Class>
 END
-        assert_includes [older, newer], assertion_message {
           @obj.to_i.to_i.to_s
         }
       end