chore: Updated aspects of Netcode package in anticipation of v2.13.4 release

[svc-netcode-sdk]

This PR was created in sync with branching of release/2.13.4. It includes changes that should land on the default Netcode branch (develop-2.0.0) to reflect the new state of the package after the v2.13.4 release:

1. Updated CHANGELOG.md by adding new [Unreleased] section template at the top and cleaning the Changelog for the current release.
2. Updated package version in package.json by incrementing the patch version to signify the current state of the package.
3. Updated package version in ValidationExceptions.json to match the new package version.

Please review and merge this PR to keep the default branch up to date with the latest package state after the release. Those changes can land immediately OR after the release was finalized but make sure that the Changelog will be merged correctly as sometimes some discrepancies may be introduced due to new entries being introduced meantime

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[u-pr]

💡 Harness Review

The change moves three existing fixes into the 2.13.4 changelog section and advances the package version to 2.13.5. I checked the changelog entries and repository version references and found no actionable issues.

_{Reviewed commit a5b2f1e}

_{🤖 Helpful? 👍/👎}

[codecov-github-com]

Codecov Report

All modified and coverable lines are covered by tests ✅

@@              Coverage Diff               @@
##           develop-2.0.0    #4190   +/-   ##
==============================================
  Coverage          74.20%   74.21%           
==============================================
  Files                172      172           
  Lines              28200    28200           
==============================================
+ Hits               20926    20928    +2     
+ Misses              7274     7272    -2     

Flag	Coverage Δ
NGOv2_project_testproject_ubuntu	73.86% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

see 1 file with indirect coverage changes

Components	Coverage Δ
com.unity.netcode.gameobjects	74.21% <ø> (+<0.01%)	⬆️

ℹ️ Need help interpreting these results?

[michalChrobot]

Cancelling as we don't have that much to release for now and we are quite focus on Unified Netcode so I will release this once we are done with those big topics (also not a lot to release so it's ok to postpone to later)