Occurrences of "pending" in starknet_ws_api.json should be addressed

[FabijanC]

Not sure what happened to #291, but the addressing of pending block changes should also include the starknet_subscribePendingTransactions web socket (ws) method:

starknet-specs/api/starknet_ws_api.json

Line 170 in f0ae2e9

"name": "starknet_subscribePendingTransactions",

Pending block is also mentioned in the same file in SUBSCRIPTION_BLOCK_ID and SUBSCRIPTION_BLOCK_TAG.

Perhaps all of these "pending" occurrences can just be renamed to "pre-confirmed".

[eitanm-starkware]

#323