Remove CLA comment from readme (foxglove#1207)

We have decided to remove the Contributor License Agreement (CLA) from
MCAP and other Foxglove open source projects. The project remains MIT
licensed, but we no longer require an additional copyright grant from
contributors 🎉.

Per the [GitHub Terms of
Service](https://docs.github.com/en/site-policy/github-terms/github-terms-of-service#6-contributions-under-repository-license),
submitted pull requests are licensed under the same terms (MIT).

<img width="540" alt="image"
src="https://github.com/user-attachments/assets/402bd612-3e57-49ab-a91a-532be882ca7e">

README.md

@@ -35,7 +35,7 @@ Download the latest `mcap-cli` version from the [releases page](https://github.c
 
 ## License
 
-[MIT License](/LICENSE). Contributors are required to accept the [Contributor License Agreement](https://github.com/foxglove/cla).
+[MIT License](/LICENSE).
 
 ## Release process