Fix clippy::let_unit_value lint in propless components

[WorldSEnder]

Description

Fixes #2931

Checklist

• I have reviewed my own code
• I have added tests.
  I can't figure out how to run clippy lints as part of the try_build macro tests. Any tip is appreciated. Otherwise, we'd have to setup another test rig just for clippy.

[github-actions]

Visit the preview URL for this PR (updated for commit 0c6238b):

https://yew-rs-api--pr2970-fix-unit-let-fm2m2jbt.web.app

_{(expires Sat, 26 Nov 2022 12:46:51 GMT)}

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[github-actions]

Benchmark - SSR

Yew Master

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	366.277	402.635	383.686	12.689
Hello World	10	707.992	744.709	717.554	11.068
Function Router	10	2376.719	2518.400	2426.456	41.827
Concurrent Task	10	1009.049	1010.577	1009.774	0.532

Pull Request

Benchmark	Round	Min (ms)	Max (ms)	Mean (ms)	Standard Deviation
Baseline	10	373.765	396.599	382.267	7.899
Hello World	10	690.043	747.658	712.212	15.654
Function Router	10	2459.871	2536.938	2505.135	25.144
Concurrent Task	10	1008.444	1010.496	1009.505	0.569

[github-actions]

Size Comparison

examples	master (KB)	pull request (KB)	diff (KB)	diff (%)
async_clock	108.684	108.683	-0.001	-0.001%
boids	172.901	172.902	+0.001	+0.001%
communication_child_to_parent	92.557	92.557	0	0.000%
communication_grandchild_with_grandparent	107.296	107.289	-0.007	-0.006%
communication_grandparent_to_grandchild	103.175	103.173	-0.002	-0.002%
communication_parent_to_child	89.663	89.663	0	0.000%
contexts	109.899	109.896	-0.004	-0.004%
counter	87.582	87.581	-0.001	-0.001%
counter_functional	88.059	88.059	0	0.000%
dyn_create_destroy_apps	90.435	90.435	0	0.000%
file_upload	102.149	102.148	-0.001	-0.001%
function_memory_game	165.372	165.372	0	0.000%
function_router	349.622	349.605	-0.017	-0.005%
function_todomvc	160.175	160.166	-0.009	-0.005%
futures	224.237	224.236	-0.001	-0.000%
game_of_life	107.107	107.107	0	0.000%
immutable	184.840	184.840	0	0.000%
inner_html	84.049	84.047	-0.002	-0.002%
js_callback	113.461	113.451	-0.010	-0.009%
keyed_list	198.071	198.069	-0.002	-0.001%
mount_point	87.191	87.193	+0.002	+0.002%
nested_list	114.186	114.188	+0.003	+0.003%
node_refs	95.057	95.057	0	0.000%
password_strength	1549.361	1549.359	-0.002	-0.000%
portals	98.521	98.522	+0.002	+0.002%
router	319.404	319.414	+0.010	+0.003%
simple_ssr	154.118	154.115	-0.003	-0.002%
ssr_router	394.606	394.601	-0.006	-0.001%
suspense	111.212	111.213	+0.001	+0.001%
timer	90.472	90.470	-0.002	-0.002%
todomvc	141.471	141.470	-0.001	-0.001%
two_apps	88.242	88.238	-0.004	-0.004%
web_worker_fib	154.486	154.478	-0.009	-0.006%
webgl	86.766	86.768	+0.002	+0.002%

✅ None of the examples has changed their size significantly.

[WorldSEnder]

@Starwort I think this should be enough to fix the clippy lints. We don't have an automated test for these lints setup, so do you mind manually testing it. At least with today's 1.67 nightly clippy, the reproduction from the bug report doesn't show any warnings for me.

[Starwort]

so do you mind manually testing it

I tried replacing, in Cargo.toml, the dependency yew = "0.19.3" with the dependency yew = { git = "https://github.com/WorldSEnder/yew", branch="fix-unit-let" }, but now I'm getting a load of compile errors including in totally unrelated places, so I can't test it in situ (that's what you were looking for, yes?)

1155 errors in openssl alone!

If you can tell me steps to repair the build, I'd be happy to post updated results; if you'd like to just run it on my codebase, the project in question is https://github.com/Starwort/gear-miner/ (the lint is disabled globally in src/app.rs) (and yes I'm aware it's full of nasty hacks)

[WorldSEnder]

It's taking a bit longer, because the app would have to be converted to yew's git version. Should not require any changes to component logic, but a few extra #[hook] annotations here and there. I am not getting errors from openssl and I can reproduce the original bug report with the repo, at least.

[hamza1311]

The openssl errors are unrelated to this change. This PR looks good so I'm going to go ahead and merge it