fix: Parse ViewModels properties always dispatch to the main queue

[cbaker6]

New Pull Request Checklist

• I am not disclosing a vulnerability.
• I am creating this PR in reference to an issue.

Issue Description

If a background task updates a Parse View Model property on the background queue, it's possible that the View connected to the property never displays the update or demonstrates weird behavior.

Related issue: #n/a

Approach

Always dispatch to the main queue when sending out notifications that a View Model property has been updated.

TODOs before merging

• Add entry to changelog
• Prepare for release

[codecov]

Codecov Report

Merging #260 (9eab08a) into main (3934a45) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #260      +/-   ##
==========================================
+ Coverage   76.79%   76.83%   +0.03%     
==========================================
  Files          98       98              
  Lines       10421    10437      +16     
==========================================
+ Hits         8003     8019      +16     
  Misses       2418     2418              

Impacted Files	Coverage Δ
Sources/ParseSwift/LiveQuery/Subscription.swift	68.35% <100.00%> (+2.60%)	⬆️
Sources/ParseSwift/Types/CloudViewModel.swift	100.00% <100.00%> (ø)
Sources/ParseSwift/Types/QueryViewModel.swift	100.00% <100.00%> (ø)

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