return false on AppConfigUnknownKeyException

[ArtificialOwl]

there is no logic in the current behavior of updateLazy() and updateSensitive that throw an AppConfigUnknownKeyException.

if there is no key in the database, there is no migration and we returns false

[nickvergessen]

Add unit test 🙊

[ArtificialOwl]

Add unit test 🙊

server/tests/lib/AppConfigTest.php

Lines 1216 to 1230 in a1b6357

	public function testUpdateLazyToLazyReturnsFalse(): void {
	$config = $this->generateAppConfig();
	$this->assertSame(false, $config->updateLazy('non-sensitive-app', 'lazy-key', true));
	}
	public function testUpdateNotLazyToNotLazyReturnsFalse(): void {
	$config = $this->generateAppConfig();
	$this->assertSame(false, $config->updateLazy('non-sensitive-app', 'non-lazy-key', false));
	}
	public function testUpdateLazyOnUnknownKeyReturnsFalse(): void {
	$config = $this->generateAppConfig();
	$this->assertSame(false, $config->updateLazy('non-sensitive-app', 'unknown-key', true));
	}

Added in #43370