Increase minimum pkg-config to 0.3.3

[palfrey]

With pkg-config <0.3.3, you get various errors as it's rather broken. 0.3.3 is the first version without those errors. The problem can be demoed as follows:

> cargo +nightly generate-lockfile -Zminimal-versions && cargo build
    Updating crates.io index
     Locking 3 packages to earliest compatible versions
      Adding cc v1.0.0 (available: v1.2.37)
      Adding libc v0.2.0 (available: v0.2.175)
      Adding pkg-config v0.3.0 (available: v0.3.32)
warning: /home/palfrey/src/remarkable/hlua/lua52-sys/Cargo.toml: no edition set: defaulting to the 2015 edition while the latest is 2024
warning: /home/palfrey/src/remarkable/hlua/hlua/Cargo.toml: no edition set: defaulting to the 2015 edition while the latest is 2024
   Compiling pkg-config v0.3.0
error[E0432]: unresolved import `std::fs::PathExt`
  --> /home/palfrey/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/pkg-config-0.3.0/src/lib.rs:60:5
   |
60 | use std::fs::PathExt;
   |     ^^^^^^^^^^^^^^^^ no `PathExt` in `fs`

error[E0554]: `#![feature]` may not be used on the stable release channel
  --> /home/palfrey/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/pkg-config-0.3.0/src/lib.rs:53:1
   |
53 | #![feature(env, path, unicode, process, fs)]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

(etc, etc on errors)