MDEV-34779: Sporadic test failure in rpl.rpl_semi_sync_cond_var_per_thd

In a merge, an mtr.call_suppression was erroneously removed
for "Got an error writing communication packets". So when
the error would expectedly occur, the test would fail.

This patch adds this suppression back.

Note that the test will still fail due MDEV-34799, which
is to be fixed in 10.6.

mysql-test/suite/rpl/r/rpl_semi_sync_cond_var_per_thd.result

@@ -1,6 +1,7 @@
 include/master-slave.inc
 [connection master]
 connection master;
+call mtr.add_suppression("Got an error writing communication packets");
 call mtr.add_suppression("Got an error reading communication packets");
 call mtr.add_suppression("Could not read packet:.* vio_errno: 1158");
 call mtr.add_suppression("Could not write packet:.* vio_errno: 1160");

mysql-test/suite/rpl/t/rpl_semi_sync_cond_var_per_thd.test

@@ -25,6 +25,7 @@
 --source include/master-slave.inc
 
 --connection master
+call mtr.add_suppression("Got an error writing communication packets");
 call mtr.add_suppression("Got an error reading communication packets");
 call mtr.add_suppression("Could not read packet:.* vio_errno: 1158");
 call mtr.add_suppression("Could not write packet:.* vio_errno: 1160");