patch 8.2.1903: buffer test fails with normal features

Problem:    Buffer test fails with normal features.
Solution:   Use 'numberwidth' instead of 'conceallevel' in the test.
diff --git a/src/testdir/test_buffer.vim b/src/testdir/test_buffer.vim
index 9ba72c5..2f0f312 100644
--- a/src/testdir/test_buffer.vim
+++ b/src/testdir/test_buffer.vim
@@ -364,11 +364,11 @@
 
 func Test_badd_options()
   new SomeNewBuffer
-  setlocal cole=3
+  setlocal numberwidth=3
   wincmd p
   badd SomeNewBuffer
   new SomeNewBuffer
-  call assert_equal(3, &cole)
+  call assert_equal(3, &numberwidth)
   close
   close
   bwipe! SomeNewBuffer