[build info]: omit symbol from top level gSP route (#92525)
When a route with params specifies `generateStaticParams`, the meaningful outputs are the sub-paths contained within. The top level route just corresponds with the file path, which isn't representative of a static or partially prerendered output. Previously it'd just inherit one of the sub-path values (ie if one path was PPRed, it'd show PPR, even if some were fully static).
This removes the symbol from those types of outputs, since #92518 moved those symbols to be within the subpaths.
For truly dynamic param cases (ie, no subpaths), the rendering symbol will still appear.
