fix(custom-element): fix that boolean prop with default true can't updated to falsy value

[lejunyang]

close #12214

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	101 kB (+166 B)	38 kB (+38 B)	34.2 kB (+86 B)
vue.global.prod.js	159 kB (+166 B)	57.9 kB (+43 B)	51.4 kB (-57 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.9 kB	18.3 kB	16.7 kB
createApp	55 kB	21.3 kB	19.4 kB
createSSRApp	59 kB	23 kB	20.9 kB
defineCustomElement	59.9 kB (+166 B)	22.9 kB (+48 B)	20.8 kB (-26 B)
overall	68.7 kB	26.3 kB	24 kB

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commit: 9cd4dda

[edison1105]

/ecosystem-ci run

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
language-tools	✅ success	✅ success
nuxt	❌ failure	✅ success
pinia	✅ success	✅ success
primevue	✅ success	✅ success
quasar	✅ success	✅ success
radix-vue	✅ success	✅ success
router	✅ success	✅ success
test-utils	✅ success	✅ success
vant	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vitepress	✅ success	✅ success
vue-i18n	✅ success	✅ success
vue-macros	✅ success	✅ success
vuetify	✅ success	✅ success
vueuse	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success

[edison1105]

/ecosystem-ci run nuxt

[vue-bot]

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
nuxt	✅ success	✅ success

[yyx990803]

Thanks for the PR! However, the fundamental reason of this bug is _setProp reflecting the attribute change causing mutation observer to be triggered again, which should be avoided in the first place.

I have reused the test from this PR in 352bc88.