Drop user deletion from 5.7 and 8.0

MySQL 5.7 and newer no longer creates the various unwanted users (root@various hosts)
that were created in older versions, so the deletion isn't needed, and only
creates extra maintenance work if any changes to the system users are made.

Author: ltangvald

5.7/docker-entrypoint.sh

@@ -143,7 +143,6 @@ if [ "$1" = 'mysqld' -a -z "$wantHelp" ]; then
 			--  or products like mysql-fabric won't work
 			SET @@SESSION.SQL_LOG_BIN=0;
 
-			DELETE FROM mysql.user WHERE user NOT IN ('mysql.session', 'mysql.sys', 'root') OR host NOT IN ('localhost') ;
 			SET PASSWORD FOR 'root'@'localhost'=PASSWORD('${MYSQL_ROOT_PASSWORD}') ;
 			GRANT ALL ON *.* TO 'root'@'localhost' WITH GRANT OPTION ;
 			${rootCreate}

8.0/docker-entrypoint.sh

@@ -143,7 +143,6 @@ if [ "$1" = 'mysqld' -a -z "$wantHelp" ]; then
 			--  or products like mysql-fabric won't work
 			SET @@SESSION.SQL_LOG_BIN=0;
 
-			DELETE FROM mysql.user WHERE user NOT IN ('mysql.infoschema', 'mysql.session', 'mysql.sys', 'root') OR host NOT IN ('localhost') ;
 			SET PASSWORD FOR 'root'@'localhost'=PASSWORD('${MYSQL_ROOT_PASSWORD}') ;
 			GRANT ALL ON *.* TO 'root'@'localhost' WITH GRANT OPTION ;
 			${rootCreate}