patch 8.1.2161: mapping test fails

Problem:    Mapping test fails.
Solution:   Run the test separately.
diff --git a/src/testdir/Make_all.mak b/src/testdir/Make_all.mak
index 68f26de..c22ce3b 100644
--- a/src/testdir/Make_all.mak
+++ b/src/testdir/Make_all.mak
@@ -375,6 +375,7 @@
 	test_makeencoding.res \
 	test_man.res \
 	test_maparg.res \
+	test_mapping.res \
 	test_marks.res \
 	test_matchadd_conceal.res \
 	test_memory_usage.res \
diff --git a/src/testdir/test_alot.vim b/src/testdir/test_alot.vim
index e3ce1e1..216ff6c 100644
--- a/src/testdir/test_alot.vim
+++ b/src/testdir/test_alot.vim
@@ -38,7 +38,6 @@
 source test_jumps.vim
 source test_lambda.vim
 source test_lispwords.vim
-source test_mapping.vim
 source test_match.vim
 source test_menu.vim
 source test_messages.vim