Fix the CI badge.

The CI badge is currently broken and just says "no status". The new CI badge is created directly from the linked CI page (3 dots, then create status badge). The actual status of the default branch is failing, which is a separate problem.

Also updated the links for the other two badges to what's currently generated from their respective sources.

RELNOTES=n/a
PiperOrigin-RevId: 712634902

README.md

@@ -1,8 +1,8 @@
 # Guava: Google Core Libraries for Java
 
-[![Latest release](https://img.shields.io/github/release/google/guava.svg)](https://github.com/google/guava/releases/latest)
-[![Build Status](https://github.com/google/guava/workflows/CI/badge.svg?branch=master)](https://github.com/google/guava/actions)
-[![OpenSSF Best Practices](https://bestpractices.coreinfrastructure.org/projects/7197/badge)](https://bestpractices.coreinfrastructure.org/projects/7197)
+[![GitHub Release](https://img.shields.io/github/v/release/google/guava)](https://github.com/google/guava/releases/latest)
+[![CI](https://github.com/google/guava/actions/workflows/ci.yml/badge.svg)](https://github.com/google/guava/actions/workflows/ci.yml)
+[![OpenSSF Best Practices](https://www.bestpractices.dev/projects/7197/badge)](https://www.bestpractices.dev/projects/7197)