chore(deps): update substrate-interface requirement

Updates the requirements on [substrate-interface](https://github.com/polkascan/py-substrate-interface) to permit the latest version.
- [Release notes](https://github.com/polkascan/py-substrate-interface/releases)
- [Commits](JAMdotTech/py-polkadot-sdk@v1.7.11...v1.8.1)

---
updated-dependencies:
- dependency-name: substrate-interface
  dependency-version: 1.8.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -2,7 +2,7 @@ bittensor~=9.9.0
 cryptography>=41.0.7,<50.0.0
 docker>=7.0.0,<8.0.0
 diskcache>=5.6.3,<6.0.0
-substrate-interface>=1.7.11,<1.8
+substrate-interface>=1.7.11,<1.9
 python-dotenv>=1.0.1,<2.0.0
 pydantic[email,timezone]>=2.0.3,<3.0.0
 pydantic-settings>=2.8.1,<3.0.0