sol-compiler update link for solc binary downloads

[gabririgo]

Expected Behavior

sol-compiler should be able to pull latest solc binanries (>0.7.2+)

new list seems to be found here: https://solc-bin.ethereum.org/bin/list.json

affected code line can be found here: 0xProject/tools#5

Current Behavior

currently fetching from https://ethereum.github.io/solc-bin/bin/list.json, which has github rate limits

Possible Solution

change link to https://solc-bin.ethereum.org/bin/list.json
another positive is it does not have rate limits, which have been affecting sol-compiler

Steps to Reproduce (for bugs)

1. run smart contract package with sol-compiler
2. use solc v.0.7.4
3. trying to compile a contract will return an error

Context

trying to upgrade package using solc 0.5.9 to 0.7.4
0.7.4 has dynamic array storage bugfix

Your Environment

| Package | Version |
| sol-compiler: | :4.1.1 -> 4.2.7 |

Network
testrpc

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[gabririgo]

Closing, as after this issue, 0x team has promptly updated and published the package