Remove redundant ctx or user_data fields (#239) #986

Job	Run time
Clippy	48s
Rustfmt	7s
Build docs	2m 24s
Test (MSRV)	1m 16s
Test (stable)	1m 51s
Test (beta)	1m 59s
Test (nightly)	2m 1s
Test (macOS)	4m 52s
Test (Windows)	4m 58s
Test (no features)	1m 3s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 10s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 13s
	23m 42s

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