fix: error message of `pop build spec` if there is a running `srtool` container

If we run the command manually to build the runtime deterministically with srtool, the docker command throws:

➜ docker run --name srtool --rm -e PACKAGE=parachain-template-runtime -e RUNTIME_DIR=./runtime -e DEFAULT_FEATURES= -e PROFILE=release -e IMAGE=c4e745adbc7d6dd0b3939a15be3a3b27d1ee6c724c2449638553b8b9fa909d75 -v /Users/chungquantin/Developer/pop-network/base-parachain:/build -v /var/folders/tb/r5r120jx4c34f2wnhrv6hx000000gn/T/cargo:/cargo-home docker.io/paritytech/srtool:1.84.1 build --app --json
docker: Error response from daemon: Conflict. The container name "/srtool" is already in use by container "14eef32e8b962cb8ea7d462288ac4f3923893ad4a5b042cecbdb3afcbc2dc4a4". You have to remove (or rename) that container to be able to reuse that name.
See 'docker run --help'.

However, pop build spec just simply throw an exit code:

◇  Would you like to build the runtime deterministically? This requires a containerization solution (Docker/Podman) and is recommended for production builds.
│  Yes
│
◇  Enter the directory path where the runtime is located:
│  ./runtime
│
┌   Pop CLI : Building your chain spec
│
◒  Building deterministic runtime...                                                                                                                                                                                  ▲  WARNING: You are using docker. It is recommend to use podman instead.
│
-└  Failed to build the deterministic runtime: IO error: command ["sh", "-c", "docker run --name srtool --rm -e PACKAGE=parachain-template-runtime -e RUNTIME_DIR=./runtime -e DEFAULT_FEATURES= -e PROFILE=release -e IMAGE=c4e745adbc7d6dd0b3939a15be3a3b27d1ee6c724c2449638553b8b9fa909d75 -v /Users/chungquantin/Developer/pop-network/base-parachain:/build -v /var/folders/tb/r5r120jx4c34f2wnhrv6hx000000gn/T/cargo:/cargo-home docker.io/paritytech/srtool:1.84.1 build --app --json"] exited with code 125
+ - Docker error: Error response from daemon: Conflict. The container name "/srtool" is already in use by container "14eef32e8b962cb8ea7d462288ac4f3923893ad4a5b042cecbdb3afcbc2dc4a4". You have to remove (or rename) that container to be able to reuse that name.