MDEV-32819: main.show_explain failed in buildbot

The testcase had a race in two places where a KILL QUERY is made towards a
running query in another connection. The query can complete early so the kill
is lost, and the test fails due to expecting ER_QUERY_INTERRUPTED.

Fix by removing the KILL QUERY. It is not needed, as the query completes by
itself after SHOW EXPLAIN FOR.
Signed-off-by: Kristian Nielsen <knielsen@knielsen-hq.org>

mysql-test/main/show_explain.result

@@ -244,9 +244,7 @@ set @foo= (select max(a) from t0 where sin(a) >0);
 connection default;
 show explain for $thr2;
 ERROR HY000: Target is not executing an operation with a query plan
-kill query $thr2;
 connection con1;
-ERROR 70100: Query execution was interrupted
 SET debug_dbug=@old_debug;
 #
 # Attempt SHOW EXPLAIN for an UPDATE
@@ -568,9 +566,14 @@ SELECT * FROM v1, t2;
 connection default;
 show explain for $thr2;
 ERROR HY000: Target is not executing an operation with a query plan
-kill query $thr2;
 connection con1;
-ERROR 70100: Query execution was interrupted
+a	b
+8	4
+8	5
+8	6
+8	7
+8	8
+8	9
 SET debug_dbug=@old_debug;
 DROP VIEW v1;
 DROP TABLE t2, t3;

mysql-test/main/show_explain.test

@@ -273,9 +273,7 @@ connection default;
 --source include/wait_condition.inc
 --error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
-evalp kill query $thr2;
 connection con1;
---error ER_QUERY_INTERRUPTED
 reap;
 SET debug_dbug=@old_debug;
 
@@ -504,9 +502,7 @@ connection default;
 --source include/wait_condition.inc
 --error ER_TARGET_NOT_EXPLAINABLE
 evalp show explain for $thr2;
-evalp kill query $thr2;
 connection con1;
---error ER_QUERY_INTERRUPTED
 reap;
 SET debug_dbug=@old_debug;
 DROP VIEW v1;