Change subgraph.yaml to use network BSC

[Tritium-VLK]

Node that I run a local graph node and define my ethereum network as bsc:http://hode.url

your subgraph.yaml specifies the network as mainnet. graphnode recommends using network bsc for bsc, so this basically always breaks. I just changed 2 lines in the package.yaml and everything worked fine.

note I also changed to start at block 5 million because we only need recent data in our local copy of the graph:

specVersion: 0.0.2
description: Pancakeswap Masterchef
schema:
  file: ./schema.graphql
dataSources:
  - kind: ethereum/contract
    name: MasterChef
    network: bsc
    source:
      address: "0x73feaa1eE314F8c655E354234017bE2193C9E24E"
      abi: MasterChef
      startBlock: 5000000
    mapping:
      kind: ethereum/events
      apiVersion: 0.0.4
      language: wasm/assemblyscript
      entities:
        - MasterChef
        - History
        - Pool
        - PoolHistory
      abis:
        - name: MasterChef
          file: ./abis/MasterChef.json
        - name: PairContract
          file: ./abis/PairContract.json
      eventHandlers:
        - event: Deposit(indexed address,indexed uint256,uint256)
          handler: deposit
        - event: Withdraw(indexed address,indexed uint256,uint256)
          handler: withdraw
      # callHandlers:
      #   - function: add(uint256,address,bool)
      #     handler: add
      #   - function: set(uint256,uint256,bool)
      #     handler: set
      #   - function: updatePool(uint256)
      #     handler: updatePool
      #   - function: dev(address)
      #     handler: dev
      file: ./src/masterchef.ts
      ```

[Tritium-VLK]

@ChefKai mind taking a look, or is there a way I can fork and submit a pr?