ci-job-capsules: test capsules/{core,extra} instead of full workspace

By running `cargo test` in /capsules, Cargo tests every crate in the
Workspace, slowing down CI unnecessarily in this step.

Makefile

@@ -465,7 +465,8 @@ ci-job-kernel:
 ci-job-capsules:
 	$(call banner,CI-Job: Capsules)
 	@# Capsule initialization depends on board/chip specific imports, so ignore doc tests
-	@cd capsules && NOWARNINGS=true RUSTFLAGS="-D warnings" TOCK_KERNEL_VERSION=ci_test cargo test --lib --examples
+	@cd capsules/core && NOWARNINGS=true RUSTFLAGS="-D warnings" TOCK_KERNEL_VERSION=ci_test cargo test --lib --examples
+	@cd capsules/extra && NOWARNINGS=true RUSTFLAGS="-D warnings" TOCK_KERNEL_VERSION=ci_test cargo test --lib --examples
 
 .PHONY: ci-job-chips
 ci-job-chips: