Change use_super_read_only default back to false

[mattlord]

Description

In this PR we change the default for the vttablet --use_super_read_only flag back to false (it was changed to true in v13 via #9312).

We are doing this because when this flag is true you may not be able to restart a replica/rdonly vttablet process. This is because:

1. The tablet has enabled super_read_only in its mysqld because it's a replica tablet.
2. When a tablet starts up, it attempts to run some DDL statements as the DBA user such as CREATE DATABASE IF NOT EXISTS _vt and that will fail with an error because the mysqld has super_read_only enabled.
3. So the tablet will not be able to come back up properly.

We really should be enabling super_read_only, both in the MySQL config file and in the tablet via this flag, as without that we will in some cases allow errant GTIDs to be generated which are then lying in wait to cause later issues. We will enable it at both layers as part of adding full super_read_only support to Vitess in #10363 (which is targeted for v15).

Related Issue(s)

• Follow-up to: Change default for super_read_only to true #9312
• Follow-up to: Revert super_read_only config file changes #10366
• Follow-up work: Task: Add full super_read_only support in Vitess #10363

Checklist

• "Backport me!" label has been added if this change should be backported
• Tests were added or are not required
• Documentation is not required as this is already reflected:

content/en/docs/13.0/reference/programs/vttablet.md:| -use_super_read_only | boolean | Set super_read_only flag when performing planned failover (default true) |
content/en/docs/14.0/reference/programs/vttablet.md:| --use_super_read_only |  | Set super_read_only flag when performing planned failover. |

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