patch 8.1.2358: tests fail on Cirrus CI for FreeBSD

Problem:    Tests fail on Cirrus CI for FreeBSD.
Solution:   Fix a test and skip some. (Christian Brabandt, closes #5281)
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index 43a9384..fb810e7 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -870,6 +870,7 @@
 endfunc
 
 func Test_terminal_composing_unicode()
+  CheckNotBSD
   let save_enc = &encoding
   set encoding=utf-8