patch 8.2.0074: Python 3 unicode test someitmes fails

Problem:    Python 3 unicode test someitmes fails.
Solution:   Make 'termencoding' empty.  Correct number of error message.

src/change.c

@@ -1218,7 +1218,7 @@ del_bytes(
     // If "count" is negative the caller must be doing something wrong.
     if (count < 1)
     {
-	siemsg("E950: Invalid count for del_bytes(): %ld", count);
+	siemsg("E292: Invalid count for del_bytes(): %ld", count);
 	return FAIL;
     }
 

src/testdir/test_python3.vim

@@ -170,11 +170,18 @@ endfunc
 
 func Test_unicode()
   " this crashed Vim once
+  let save_tenc = &tenc
+  set tenc=
+
   set encoding=utf32
   py3 print('hello')
+
   set encoding=debug
   py3 print('hello')
+
   set encoding=euc-tw
   py3 print('hello')
+
   set encoding=utf8
+  let &tenc = save_tenc
 endfunc

src/version.c

@@ -742,6 +742,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    74,
 /**/
     73,
 /**/