patch 8.2.4611: typos in tests; one lua line not covered by test

Problem:    Typos in tests; one lua line not covered by test.
Solution:   Fix typos. Add test case. (Dominique Pellé, closes #9994)
diff --git a/src/testdir/test_crypt.vim b/src/testdir/test_crypt.vim
index f43c22a..f3750b3 100644
--- a/src/testdir/test_crypt.vim
+++ b/src/testdir/test_crypt.vim
@@ -172,7 +172,7 @@
   call assert_equal(range(1, 4000)->map( {_, v -> string(v)}), getline(1,'$'))
   set key=
   w! ++ff=unix
-  " enryption removed (on MS-Windows the .* matches [unix])
+  " encryption removed (on MS-Windows the .* matches [unix])
   call assert_match('"Xcrypt_sodium.txt".*4000L, 18893B written', execute(':message'))
   bw!
   call delete('Xcrypt_sodium.txt')