patch 8.2.0156: various typos in source files and tests

Problem:    Various typos in source files and tests.
Solution:   Fix the typos. (Emir Sari, closes #5532)
diff --git a/src/testdir/test_edit.vim b/src/testdir/test_edit.vim
index 4e29e7f..1a37146 100644
--- a/src/testdir/test_edit.vim
+++ b/src/testdir/test_edit.vim
@@ -589,7 +589,7 @@
   call feedkeys("A\<c-x>\<c-k>\<down>\<down>\<down>\<down>\<cr>\<esc>", 'tnix')
   call assert_equal(['AA'], getline(1, '$'))
 
-  " press an unexecpted key after dictionary completion
+  " press an unexpected key after dictionary completion
   %d
   call setline(1, 'A')
   call cursor(1, 1)