chore: remove redundant symbol in contracts/scripts/oracle/README.md

[xixishidibei]

Code Change Checklist

To be completed before internal review begins:

• [ ] The contract code is complete
• [ ] Executable deployment file
• [ ] Fork tests that test after the deployment file runs
• [ ] Unit tests *if needed
• [ ] The owner has done a full checklist review of the code + tests

Internal review:

• [ ] Two approvals by internal reviewers

Deploy checklist

Two reviewers complete the following checklist:

- [ ] All deployed contracts are listed in the deploy PR's description
- [ ] Deployed contract's verified code (and all dependencies) match the code in master
- [ ] The transactions that interacted with the newly deployed contract match the deploy script.
- [ ] Governance proposal matches the deploy script
- [ ] Smoke tests pass after fork test execution of the governance proposal