Remove `build_container.sh` script (replaced by more capable `eessi_container.sh`)

[bedroge]

It has been replaced by eessi_container.sh.

[eessi-bot[bot]]

Instance eessi-bot-mc-aws is configured to build:

• arch x86_64/generic for repo eessi-hpc.org-2023.06-compat
• arch x86_64/generic for repo eessi-hpc.org-2023.06-software
• arch x86_64/generic for repo eessi.io-2023.06-compat
• arch x86_64/generic for repo eessi.io-2023.06-software
• arch x86_64/intel/haswell for repo eessi-hpc.org-2023.06-compat
• arch x86_64/intel/haswell for repo eessi-hpc.org-2023.06-software
• arch x86_64/intel/haswell for repo eessi.io-2023.06-compat
• arch x86_64/intel/haswell for repo eessi.io-2023.06-software
• arch x86_64/intel/skylake_avx512 for repo eessi-hpc.org-2023.06-compat
• arch x86_64/intel/skylake_avx512 for repo eessi-hpc.org-2023.06-software
• arch x86_64/intel/skylake_avx512 for repo eessi.io-2023.06-compat
• arch x86_64/intel/skylake_avx512 for repo eessi.io-2023.06-software
• arch x86_64/amd/zen2 for repo eessi-hpc.org-2023.06-compat
• arch x86_64/amd/zen2 for repo eessi-hpc.org-2023.06-software
• arch x86_64/amd/zen2 for repo eessi.io-2023.06-compat
• arch x86_64/amd/zen2 for repo eessi.io-2023.06-software
• arch x86_64/amd/zen3 for repo eessi-hpc.org-2023.06-compat
• arch x86_64/amd/zen3 for repo eessi-hpc.org-2023.06-software
• arch x86_64/amd/zen3 for repo eessi.io-2023.06-compat
• arch x86_64/amd/zen3 for repo eessi.io-2023.06-software
• arch aarch64/generic for repo eessi-hpc.org-2023.06-compat
• arch aarch64/generic for repo eessi-hpc.org-2023.06-software
• arch aarch64/generic for repo eessi.io-2023.06-compat
• arch aarch64/generic for repo eessi.io-2023.06-software
• arch aarch64/neoverse_n1 for repo eessi-hpc.org-2023.06-compat
• arch aarch64/neoverse_n1 for repo eessi-hpc.org-2023.06-software
• arch aarch64/neoverse_n1 for repo eessi.io-2023.06-compat
• arch aarch64/neoverse_n1 for repo eessi.io-2023.06-software
• arch aarch64/neoverse_v1 for repo eessi-hpc.org-2023.06-compat
• arch aarch64/neoverse_v1 for repo eessi-hpc.org-2023.06-software
• arch aarch64/neoverse_v1 for repo eessi.io-2023.06-compat
• arch aarch64/neoverse_v1 for repo eessi.io-2023.06-software

[boegel]

There goes my muscle memory 😅

(I don't oppose removing the script, to be clear, doesn't make sense to have two scripts that roughly have the same purpose)