Revert "logmsg_reencode(): warn when iconv() fails"

This reverts commit fd680bc5 (logmsg_reencode(): warn when iconv()
fails, 2021-08-27).  Throwing a warning for each and every commit
that gets reencoded, without allowing a way to squelch, would make
it unpleasant for folks who have to deal with an ancient part of the
history in an old project that used wrong encoding in the commits.

Documentation/pretty-options.txt

@@ -40,9 +40,7 @@ people using 80-column terminals.
 	defaults to UTF-8. Note that if an object claims to be encoded
 	in `X` and we are outputting in `X`, we will output the object
 	verbatim; this means that invalid sequences in the original
-	commit may be copied to the output. Likewise, if iconv(3) fails
-	to convert the commit, we will output the original object
-	verbatim, along with a warning.
+	commit may be copied to the output.
 
 --expand-tabs=<n>::
 --expand-tabs::

pretty.c

@@ -671,11 +671,7 @@ const char *repo_logmsg_reencode(struct repository *r,
 	 * If the re-encoding failed, out might be NULL here; in that
 	 * case we just return the commit message verbatim.
 	 */
-	if (!out) {
-		warning("unable to reencode commit to '%s'", output_encoding);
-		return msg;
-	}
-	return out;
+	return out ? out : msg;
 }
 
 static int mailmap_name(const char **email, size_t *email_len,

t/t4210-log-i18n.sh

@@ -131,11 +131,4 @@ do
 	fi
 done
 
-test_expect_success 'log shows warning when conversion fails' '
-	enc=this-encoding-does-not-exist &&
-	git log -1 --encoding=$enc 2>err &&
-	echo "warning: unable to reencode commit to ${SQ}${enc}${SQ}" >expect &&
-	test_cmp expect err
-'
-
 test_done