[BUGFIX] Fix reference to RST file for GU:hmac deprecation

With #102762, `GeneralUtility::hmac()` has been deprecated. The
change also added a method call match for the extension scanner,
which however refers to the wrong RST file.

This change fixes the wrong RST reference.

Resolves: #104260
Related: #102762
Releases: main
Change-Id: I7e0fd8a871198bc66ffa13a1adb994a2c3c4ed48
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/85009


Reviewed-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Jasmina Ließmann <minapokhalo+typo3@gmail.com>
Tested-by: core-ci <typo3@b13.com>