chore: drop unused reqwest http3 feature and reqwest_unstable flag

Probes now use quinn/h3 directly and the Mimir push is HTTP/1.1 or HTTP/2,
so reqwest's http3 feature is unused. Removing it also removes the need for
the `--cfg reqwest_unstable` build flag, so drop it from the Dockerfile.

The RUSTFLAGS export in devbox.json is left alone (it carries an unrelated
pending change); the flag is now a harmless no-op there and can be removed
with that change.

Author: tluijken

oxybox/Cargo.toml

@@ -14,7 +14,7 @@ edition = "2024"
 
 [dependencies]
 tokio = { version = "1", features = ["full"] }
-reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls", "http2", "http3"] }
+reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls", "http2"] }
 x509-parser = "0.18"
 url = "2"
 prost = "0.14"

oxybox/Dockerfile

@@ -1,9 +1,6 @@
 # Dockerfile for building the Oxybox application using Rust and musl
 FROM clux/muslrust:stable
 
-# Set the environment variables for the build
-# We're using the reqwest unstable feature HTTP3
-ENV RUSTFLAGS='--cfg reqwest_unstable'
 RUN mkdir /source
 WORKDIR /source
 COPY ./Cargo.toml .