patch 9.1.0220: Few typos in source and test files

Problem:  Typos in code and tests.
Solution: Fix typos (zeertzjq).

closes: #14321

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index 78d301f..914d1e3 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -708,11 +708,11 @@
 
 func Test_mkview_no_file_name()
   new
-  " :mkview or :mkview {nr} should fail in a unnamed buffer.
+  " :mkview or :mkview {nr} should fail in an unnamed buffer.
   call assert_fails('mkview', 'E32:')
   call assert_fails('mkview 1', 'E32:')
 
-  " :mkview {file} should succeed in a unnamed buffer.
+  " :mkview {file} should succeed in an unnamed buffer.
   mkview Xview
   help
   source Xview