patch 9.1.1223: wrong translation used for encoding failures

Problem:  wrong translation for encoding failures because of using
          literal "from" and "to" in the resulting error message
          (RestorerZ)
Solution: use separate error messages for errors "from" and "to"
          encoding errors.

fixes: #16898
closes: #16918

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_functions.vim b/src/testdir/test_functions.vim
index 724fda0..c498ec0 100644
--- a/src/testdir/test_functions.vim
+++ b/src/testdir/test_functions.vim
@@ -4422,10 +4422,10 @@
 
     call assert_fails("call str2blob(['abc'], [])", 'E1206: Dictionary required for argument 2')
     call assert_fails("call str2blob(['abc'], {'encoding': []})", 'E730: Using a List as a String')
-    call assert_fails("call str2blob(['abc'], {'encoding': 'ab12xy'})", 'E1515: Unable to convert to ''ab12xy'' encoding')
-    call assert_fails("call str2blob(['ŝş'], {'encoding': 'latin1'})", 'E1515: Unable to convert to ''latin1'' encoding')
-    call assert_fails("call str2blob(['அஇ'], {'encoding': 'latin1'})", 'E1515: Unable to convert to ''latin1'' encoding')
-    call assert_fails("call str2blob(['🁰🁳'], {'encoding': 'latin1'})", 'E1515: Unable to convert to ''latin1'' encoding')
+    call assert_fails("call str2blob(['abc'], {'encoding': 'ab12xy'})", 'E1516: Unable to convert to ''ab12xy'' encoding')
+    call assert_fails("call str2blob(['ŝş'], {'encoding': 'latin1'})", 'E1516: Unable to convert to ''latin1'' encoding')
+    call assert_fails("call str2blob(['அஇ'], {'encoding': 'latin1'})", 'E1516: Unable to convert to ''latin1'' encoding')
+    call assert_fails("call str2blob(['🁰🁳'], {'encoding': 'latin1'})", 'E1516: Unable to convert to ''latin1'' encoding')
   END
   call v9.CheckLegacyAndVim9Success(lines)
 endfunc