MDEV-8020: innodb.innodb-mdev-7055 produces valgrind warnings in buildbot

Fixed by reverting incorrect fix of MDEC-7055 (reopened) and removing the
test case (because it now crashes).

mysql-test/suite/innodb/r/innodb-mdev-7055.result

-1

mysql-test/suite/innodb/t/innodb-mdev-7055.test

--- source include/have_innodb.inc
-
-# MDEV-7055: MySQL#74664 - InnoDB: Failing assertion: len <= col->len 
-# || col->mtype == 5 || (col->len == 0 && col->mtype == 1) in 
-# file rem0rec.cc line 845
---disable_query_log
---disable_warnings
---disable_result_log
-set @old_character_set=@@character_set_connection;
-set character_set_connection=ucs2;
-create TABLE t1 engine=innodb select if(0=0,'Y','N');
-insert INTO t1 values(date_format('2001-01-01','%W'));
-select * from t1;
-drop table t1;
-set @@character_set_connection=@old_character_set;
---enable_result_log
---enable_warnings
---enable_query_log
-
-#produce something
---echo 1
-
-

storage/innobase/rem/rem0rec.c

@@ -830,8 +830,7 @@ rec_get_converted_size_comp_prefix_low(
 		}
 
 		ut_ad(len <= col->len || col->mtype == DATA_BLOB
-			|| col->mtype == DATA_VARMYSQL
-			|| (col->len == 0 && col->mtype == DATA_VARCHAR));
+		      || (col->len == 0 && col->mtype == DATA_VARCHAR));
 
 		fixed_len = field->fixed_len;
 		if (temp && fixed_len
@@ -1258,8 +1257,7 @@ rec_convert_dtuple_to_rec_comp(
 			*lens-- = (byte) len;
 		} else {
 			ut_ad(len <= dtype_get_len(type)
-				|| dtype_get_mtype(type) == DATA_BLOB
-				|| dtype_get_mtype(type) == DATA_VARMYSQL);
+				|| dtype_get_mtype(type) == DATA_BLOB);
 			if (len < 128
 			    || (dtype_get_len(type) < 256
 				&& dtype_get_mtype(type) != DATA_BLOB)) {

storage/xtradb/rem/rem0rec.c

@@ -830,7 +830,6 @@ rec_get_converted_size_comp_prefix_low(
 		}
 
 		ut_ad(len <= col->len || col->mtype == DATA_BLOB
-			|| col->mtype == DATA_VARMYSQL
 			|| (col->len == 0 && col->mtype == DATA_VARCHAR));
 
 		fixed_len = field->fixed_len;
@@ -1258,8 +1257,7 @@ rec_convert_dtuple_to_rec_comp(
 			*lens-- = (byte) len;
 		} else {
 			ut_ad(len <= dtype_get_len(type)
-				|| dtype_get_mtype(type) == DATA_BLOB
-				|| dtype_get_mtype(type) == DATA_VARMYSQL);
+				|| dtype_get_mtype(type) == DATA_BLOB);
 			if (len < 128
 			    || (dtype_get_len(type) < 256
 				&& dtype_get_mtype(type) != DATA_BLOB)) {