test/ruby/test_string.rb: skip test_crypt for MJIT again

Partially reverting r65285. Actually this one is failing due to memory
consumption on MJIT, so this seems not catching the bug of MJIT.

test/ruby/test_io.rb: unify the skip message with it

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65309 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_io.rb

@@ -3823,7 +3823,7 @@ __END__
   end
 
   def test_select_leak
-    skip 'MJIT uses too much memory' if RubyVM::MJIT.enabled?
+    skip 'assert_no_memory_leak may consider MJIT memory usage as leak' if RubyVM::MJIT.enabled?
     # avoid malloc arena explosion from glibc and jemalloc:
     env = {
       'MALLOC_ARENA_MAX' => '1',

test/ruby/test_string.rb

@@ -647,6 +647,7 @@ CODE
   end
 
   def test_crypt
+    skip 'assert_no_memory_leak may consider MJIT memory usage as leak' if RubyVM::MJIT.enabled?
     assert_equal(S('aaGUC/JkO9/Sc'), S("mypassword").crypt(S("aa")))
     assert_not_equal(S('aaGUC/JkO9/Sc'), S("mypassword").crypt(S("ab")))
     assert_raise(ArgumentError) {S("mypassword").crypt(S(""))}