Remove the below pages

[SangeetaMishr]

We have clubbed these sections on one doc ( #446)

Google Cloud Storage Setup - https://glific.github.io/docs/docs/Pre%20Onboarding/GCS%20Setup/Google%20Cloud%20Storage%20Setup

GCS Setup with UPI - https://glific.github.io/docs/docs/Pre%20Onboarding/GCS%20Setup/GCS%20Setup%20with%20UPI