patch 8.2.0075: Python 3 unicode test still sometimes fails

Problem:    Python 3 unicode test still sometimes fails.
Solution:   Skip the test when 'termencoding' is not empty.

src/testdir/test_python3.vim

@@ -170,8 +170,9 @@ endfunc
 
 func Test_unicode()
   " this crashed Vim once
-  let save_tenc = &tenc
-  set tenc=
+  if &tenc != ''
+    throw "Skipped: 'termencoding' is not empty"
+  endif
 
   set encoding=utf32
   py3 print('hello')
@@ -183,5 +184,4 @@ func Test_unicode()
   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 */
+/**/
+    75,
 /**/
     74,
 /**/