chore(cargo): upgrade proc-macro2 v1.0.56 -> v1.0.95

[ardnew]

Description

Update proc-macro2 in Cargo.lock by running cargo update -p proc-macro2.

Reason

rust nightly >= 2023-06-28 removed a compiler feature that proc-macro2 v1.0.56 uses.

This has already been fixed upstream.

It has also been mentioned in rust-lang/rust#113152

Notes

cargo 1.88.0-nightly (d811228b1 2025-04-15)
release: 1.88.0-nightly
commit-hash: d811228b14ae2707323f37346aee3f4147e247e6
commit-date: 2025-04-15
host: x86_64-unknown-linux-gnu
libgit2: 1.9.0 (sys:0.20.0 vendored)
libcurl: 8.12.1-DEV (sys:0.4.80+curl-8.12.1 vendored ssl:OpenSSL/3.4.1)
ssl: OpenSSL 3.4.1 11 Feb 2025
os: Ubuntu 24.10.0 (oracular) [64-bit]

Building system76-scheduler in the environment above with proc-macro2 v1.0.56 results in the following error:

$ just execsnoop=$(which execsnoop-bpfcc) build-release
env EXECSNOOP_PATH=/usr/sbin/execsnoop-bpfcc cargo build --release
  (...snip...)
error[E0635]: unknown feature `proc_macro_span_shrink`
  --> /opt/rust/cargo/registry/src/index.crates.io-1949cf8c6b5b557f/proc-macro2-1.0.56/src/lib.rs:92:30
   |
92 |     feature(proc_macro_span, proc_macro_span_shrink)
   |                              ^^^^^^^^^^^^^^^^^^^^^^

[jacobgkau]

Regression testing passed:

• Focus-based assignments are working with the default config (both .debs and Flatpaks).
• Focus-based assignments work with custom values in /etc.
• nice -n # works with the default config.
• A custom profile with no niceness defined still has foreground/background applied.
  • Only applied at launch. (Not a regression.)
• A custom profile with a niceness defined inline (under process-scheduler/) works.
• A custom profile with a niceness defined separately (in config.kdl) works.
• Config reloading works with system76-scheduler daemon reload, systemctl reload com.system76.Scheduler.service, and systemctl restart com.system76.Scheduler.service.
• PipeWire integration works; when an app starts playing audio, it's assigned the niceness of the pipewire group and retains it until it's closed. It gets regular foreground/background niceness again when it's relaunched (or sooner if the audio stream stops.)
• After disabling the foreground/background profiles, other profiles still work.

The failing Focal build is not a problem because we have a separate master_focal branch that this PR will not affect.