Background

v8.5.7 requires Go 1.25.10 across components. TiCDC release-8.5 should update its Go version declarations, README build instructions, and CI integration-test Go toolchain from 1.25.8 to 1.25.10.

Scope

• Update Go directive in release-8.5 module files to 1.25.10.
• Update integration-test Dockerfile Go toolchain version to 1.25.10.
• Update README Go installation instructions to 1.25.10.
• Keep dependency versions unchanged unless go mod tidy requires otherwise.

Target branch

release-8.5