docs(container-pull): remove LTS tag verbiage

[carlosmmatos-cs]

Summary

• remove LTS and LTS-1 from documented version channel options
• replace LTS examples with supported N-2 guidance
• remove LTS references from script help and runtime tips
• leave the underlying version resolution logic unchanged

Testing

• shfmt checks for Bash and POSIX modes
• ShellCheck checks for Bash and dash
• bash tests/test-version-channels.sh (31 passed)
• git diff --check