patch 8.1.1826: tests use hand coded feature and option checks

Problem:    Tests use hand coded feature and option checks.
Solution:   Use the commands from check.vim in more tests.
diff --git a/src/testdir/test_memory_usage.vim b/src/testdir/test_memory_usage.vim
index debc9c1..d7c7036 100644
--- a/src/testdir/test_memory_usage.vim
+++ b/src/testdir/test_memory_usage.vim
@@ -2,10 +2,8 @@
 
 source check.vim
 CheckFeature terminal
+CheckNotGui
 
-if has('gui_running')
-  throw 'Skipped: does not work in GUI'
-endif
 if execute('version') =~# '-fsanitize=[a-z,]*\<address\>'
   " Skip tests on Travis CI ASAN build because it's difficult to estimate
   " memory usage.