Resolve @grpc/proto-loader to ^0.7.8

[amgleitman]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

Resolve @grpc/proto-loader to ^0.7.8.

This version resolves a security issue with protobufjs.

Changelog

[Internal] [Security] - Security updates

Test Plan

If the CIs pass, we should be good

[github-actions]

	Warnings
⚠️	🔒 package.json - Changes were made to package.json. This will require a manual import by a Facebook employee.

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