Documentation of --symbols-path is wrong

[Robin Lambertz]

Currently, the documentation claims that we can "provide those symbol files directly as symbols-path values (passed positionally, see the cli manual below)", or that they're a "Path to a symbol file.". However, looking at what the code does, it looks like --symbols-path is treated as a directory where symbols are looked up by looking at {path}/{pdbname}.pdb/{id}/{pdbname}.sym: https://github.com/rust-minidump/rust-minidump/blob/main/breakpad-symbols/src/lib.rs#L452

This is very confusing, and not very practical. It'd be better if --symbol-path took the sym file directly, rather than forcing a directory layout.