[voice] remove unused stt events (#2741)

Signed-off-by: Miguel Álvarez Díez <miguelwork92@gmail.com>

bundles/org.openhab.core.voice/src/main/java/org/openhab/core/voice/SpeechStartEvent.java

@@ -1,24 +0,0 @@
-/**
- * Copyright (c) 2010-2022 Contributors to the openHAB project
- *
- * See the NOTICE file(s) distributed with this work for additional
- * information.
- *
- * This program and the accompanying materials are made available under the
- * terms of the Eclipse Public License 2.0 which is available at
- * http://www.eclipse.org/legal/epl-2.0
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-package org.openhab.core.voice;
-
-import org.eclipse.jdt.annotation.NonNullByDefault;
-
-/**
- * A {@link STTEvent} fired when the {@link STTService} starts hearing speech.
- *
- * @author Kelly Davis - Initial contribution
- */
-@NonNullByDefault
-public class SpeechStartEvent implements STTEvent {
-}

bundles/org.openhab.core.voice/src/main/java/org/openhab/core/voice/SpeechStopEvent.java

@@ -1,24 +0,0 @@
-/**
- * Copyright (c) 2010-2022 Contributors to the openHAB project
- *
- * See the NOTICE file(s) distributed with this work for additional
- * information.
- *
- * This program and the accompanying materials are made available under the
- * terms of the Eclipse Public License 2.0 which is available at
- * http://www.eclipse.org/legal/epl-2.0
- *
- * SPDX-License-Identifier: EPL-2.0
- */
-package org.openhab.core.voice;
-
-import org.eclipse.jdt.annotation.NonNullByDefault;
-
-/**
- * A {@link STTEvent} fired when the {@link STTService} stops hearing speech.
- *
- * @author Kelly Davis - Initial contribution
- */
-@NonNullByDefault
-public class SpeechStopEvent implements STTEvent {
-}