Sync search-service property name from release pom to site-toolkit

The release pom defines:

<hippo.addon-search-service.version>100.4.0-SNAPSHOT</hippo.addon-search-service.version>

In the site-toolkit for the same dependency another property name is used:

<hippo.services.search.version>100.4.0-SNAPSHOT</hippo.services.search.version>

Although 'addon-search-service' is not the best description, use that name as it's defined in the release pom and used elsewhere.