Rework links in platform docs to account for new landing pages

[TC-MO]

Since new landing pages for:

SDK - docs.apify.com/sdk API - docs.apify.com/api

Have been released, there is a need to rework the prose in part of documentation and links, to link to those landing pages instead of specific clients or SDKs.

Steps:

1. Find all the places where we link to the specific pages for SDKs/APIs
2. Rework the prose
3. Link to the landing pages