cargo: switch from proc-macro pin-project to declarative pin-project-lite

In our simple use cases they both should generate the same code, see
[0] for notable differences. While we cannot drop proc-macro due to
that switch, all of our dependencies that use pinning already use
pin-project-lite, so this allows us to drop a whole crate in general
while not loosing anything.

[0]: https://github.com/taiki-e/pin-project-lite#pin-project-vs-pin-project-lite

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

pbs-client/Cargo.toml

@@ -18,7 +18,7 @@ libc = "0.2"
 nix = "0.19.1"
 openssl = "0.10"
 percent-encoding = "2.1"
-pin-project = "1.0"
+pin-project-lite = "0.2"
 regex = "1.2"
 rustyline = "7"
 serde_json = "1.0"