Exclude defmt-test from cargo-semver-checks

defmt-test now depends on the semihosting crate, which cannot compile
on x86_64. This prevents cargo-semver-checks from running cargo-doc on
the host

Signed-off-by: Siddhant Pandit <70386749+Siddhant779@users.noreply.github.com>

Author: Siddhant779

.github/workflows/cargo-semver-check.yml

@@ -39,5 +39,5 @@ jobs:
         uses: obi1kenobi/cargo-semver-checks-action@v2
         with:
           manifest-path: firmware/
-          exclude: defmt-semihosting
+          exclude: defmt-semihosting,defmt-test
           # rust-target: thumbv7em-none-eabihf