Remove redundant ctx or user_data fields (#239) #981

Job	Run time
Clippy	43s
Test (MSRV)	1m 21s
Rustfmt	30s
Test (stable)	1m 59s
Build docs	2m 19s
Test (beta)	1m 55s
Test (nightly)	2m 4s
Test (macOS)	4m 58s
Test (Windows)	4m 51s
Test (no features)	1m 9s
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 25s
	24m 24s

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