fix(`sol!`)!: gen unit struct for no param events #2362

Job	Run time
check no_std	37s
test ubuntu-latest stable --no-default-features	58s
features stable	1m 32s
miri --no-default-features	5m 27s
miri	5m 37s
test ubuntu-latest stable	59s
features stable --all-targets	2m 52s
miri --all-features	8m 27s
test ubuntu-latest nightly --no-default-features	47s
wasm	26s
features nightly	1m 35s
test ubuntu-latest nightly	47s
features nightly --all-targets	2m 57s
clippy	55s
test ubuntu-latest 1.81 --no-default-features	37s
test ubuntu-latest 1.81	40s
docs	29s
fmt	15s
test windows-latest stable --no-default-features	1m 59s
test windows-latest stable	2m 31s
test windows-latest nightly --no-default-features	2m 12s
test windows-latest nightly	2m 10s
test windows-latest 1.81 --no-default-features	1m 19s
test windows-latest 1.81	1m 19s
test ubuntu-latest 1.81 --features json	41s
test windows-latest 1.81 --features json	1m 17s
test ubuntu-latest nightly --all-features	1m 11s
test windows-latest nightly --all-features	2m 40s
deny / cargo deny check	21s
ci success	2s
	53m 39s

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