With the new git-hooks submodule, all of our hooks can live in a single
place. So README.md should tell users to use that location instead of
using curl commands.

Bug: b/187094215
Change-Id: Ibcb058e73a0ed0fec182da23345b6282eb5df6c0
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/54688
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Sean Risser <srisser@google.com>
Commit-Queue: Sean Risser <srisser@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>