Remove redundant fields from Context #1137

Job	Run time
Build docs	1m 19s
Clippy	55s
Rustfmt	13s
Test (MSRV)	1m 14s
Test (stable)	1m 59s
Test (beta)	2m 1s
Test (nightly)	1m 47s
Test (macOS)	1m 32s
Test (Windows)	4m 6s
Test (no features)	1m 15s
Test (all features - simdjson, cargo test --all-features --lib --tests --examples)	1m 11s
Test (native TLS, cargo test --all-features --features serenity/native_tls_backend --lib --tests ...	1m 21s
	18m 53s

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