[8.11] [Fleet] Remove agent upgrade fix from 8.11.1 release notes (#171200) (#171249)

# Backport

This will backport the following commits from `main` to `8.11`:
- [[Fleet] Remove agent upgrade fix from 8.11.1 release notes
(#171200)](https://github.com/elastic/kibana/pull/171200)

<!--- Backport version: 8.9.7 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Kyle
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Remove agent upgrade fix from 8.11.1 release notes (#171200)\n\n##
Summary\r\n\r\nThe 8.11.1 release notes included #170974 which didn't
actually land in\r\n8.11.1. We shipped BC2 of 8.11.1 which was built
from this
Kibana\r\ncommit:\r\n09feaf416f.\r\nThe
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8.11.1.\r\n\r\nThis PR removes the erroneous release note from the
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Remove agent upgrade fix from 8.11.1 release notes (#171200)\n\n##
Summary\r\n\r\nThe 8.11.1 release notes included #170974 which didn't
actually land in\r\n8.11.1. We shipped BC2 of 8.11.1 which was built
from this
Kibana\r\ncommit:\r\n09feaf416f.\r\nThe
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Remove agent upgrade fix from 8.11.1 release notes (#171200)\n\n##
Summary\r\n\r\nThe 8.11.1 release notes included #170974 which didn't
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from this
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BACKPORT-->

Co-authored-by: Kyle Pollich <kyle.pollich@elastic.co>

docs/CHANGELOG.asciidoc

@@ -81,7 +81,6 @@ announcement].
 === Bug Fixes
 
 Fleet::
-* Fixes inability to upgrade agents from version 8.10.4 to version 8.11 ({kibana-pull}170974[#170974]).
 * Append space ID to security solution tag ({kibana-pull}170789[#170789]).
 * Modify bulk unenroll to include inactive agents ({kibana-pull}170249[#170249]).
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