fix: backwards compatibility for setting agent schedule status

[lowlydba]

Description

Increase backwards compatibility for older DbaTools versions by only using the Disabled parameter and not the Enabled parameter which may not have always been valid.

How Has This Been Tested?

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue) - Fixes #197
• [ ] New feature (non-breaking change which adds functionality)

Checklist:

• [x] I have read/followed the CONTRIBUTING document.
• [x] I have read/followed the PR Quick Start Guide
• [x] I have added tests to cover my changes or they are N/A.
• [x] I have added a changelog fragment describing the changes.
• [ ] New module options/parameters include a version_added property.

[codecov-commenter]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (f78faaf) 93.68% compared to head (416e9c0) 89.38%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #210 +/- ## ========================================== - Coverage 93.68% 89.38% -4.31% ========================================== Files 64 52 -12 Lines 2202 1451 -751 ========================================== - Hits 2063 1297 -766 - Misses 139 154 +15 ``` | [Flag](https://app.codecov.io/gh/lowlydba/lowlydba.sqlserver/pull/210/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=John+McCall) | Coverage Δ | | |---|---|---| | [sanity](https://app.codecov.io/gh/lowlydba/lowlydba.sqlserver/pull/210/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=John+McCall) | `100.00% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=John+McCall#carryforward-flags-in-the-pull-request-comment) to find out more. [see 15 files with indirect coverage changes](https://app.codecov.io/gh/lowlydba/lowlydba.sqlserver/pull/210/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=John+McCall)

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