Update shlex dependency to version 2

[musicinmybrain]

See https://github.com/comex/rust-shlex/blob/653936e120cdd0a8d1b4f0837e2cce0f347da4c0/CHANGELOG.md. There are only three calls into shlex, and they don’t use any of the APIs that were removed in v2:

podlet/src/escape.rs

Line 36 in 74ba158

shlex::try_quote(&arg)

podlet/src/escape.rs

Line 41 in 74ba158

shlex::try_quote(arg).expect("string does not contain null character")

podlet/src/cli/compose.rs

Line 32 in 74ba158

Command::String(command) => shlex::split(&command)

[k9withabone]

Looks good! Thanks!