Extend dummy factory in tests

Signed-off-by: Julius Härtl <jus@bitgrid.net>

tests/lib/Share20/ManagerTest.php

@@ -4362,6 +4362,9 @@ class DummyFactory implements IProviderFactory {
 	public function getAllProviders() {
 		return [$this->provider];
 	}
+
+	public function registerProvider(string $shareProvier): void {
+	}
 }
 
 class DummyFactory2 extends DummyFactory {
@@ -4378,4 +4381,7 @@ class DummyFactory2 extends DummyFactory {
 	public function getAllProviders() {
 		return [$this->provider, $this->provider2];
 	}
+
+	public function registerProvider(string $shareProvier): void {
+	}
 }