[TASK] Pin fluid standalone dependency to ^2.6.10

Various parts of TYPO3 Core are not ready yet
to be used with Fluid Engine 3.0-dev, which
people might accidentally install.

This change sets the fluid dependency back to
^2.6.10

Used commands:

- composer req "typo3fluid/fluid:^2.6.10"
- composer req "typo3fluid/fluid:^2.6.10" -d typo3/sysext/adminpanel --no-update
- composer req "typo3fluid/fluid:^2.6.10" -d typo3/sysext/core --no-update
- composer req "typo3fluid/fluid:^2.6.10" -d typo3/sysext/fluid --no-update
- composer req "typo3fluid/fluid:^2.6.10" -d typo3/sysext/redirects --no-update

Resolves: #91850
Releases: master, 10.4
Change-Id: If46475fd3fdbca3ce23a652a253c0ac28d9a6149
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68919


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Oliver Bartsch <bo@cedev.de>
Reviewed-by: Benjamin Franzke <bfr@qbus.de>
Tested-by: core-ci <typo3@b13.com>
Tested-by: Oliver Bartsch <bo@cedev.de>
Tested-by: Benjamin Franzke <bfr@qbus.de>