[TASK] EXT:redirects - Wrong variable name in phpdoc of class SourceHost

- Resolves a wrong variable definition in phpdoc
- Adds type safe method parameter
- Adds return type string to method

Resolves: #83665
Releases: master
Change-Id: I0ed52e0b2086d6d006885964f480b3c99b7942e7
Reviewed-on: https://review.typo3.org/55440


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Henning Liebe <h.liebe@neusta.de>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>