Add missing 'final' in Java classes

For consistency.

server/src/main/java/com/genymobile/scrcpy/wrappers/ActivityManager.java

@@ -17,7 +17,7 @@ import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
 @SuppressLint("PrivateApi,DiscouragedPrivateApi")
-public class ActivityManager {
+public final class ActivityManager {
 
     private final IInterface manager;
     private Method getContentProviderExternalMethod;

server/src/main/java/com/genymobile/scrcpy/wrappers/ClipboardManager.java

@@ -11,7 +11,7 @@ import android.os.IInterface;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
-public class ClipboardManager {
+public final class ClipboardManager {
     private final IInterface manager;
     private Method getPrimaryClipMethod;
     private Method setPrimaryClipMethod;

server/src/main/java/com/genymobile/scrcpy/wrappers/ContentProvider.java

@@ -14,7 +14,7 @@ import java.io.Closeable;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
-public class ContentProvider implements Closeable {
+public final class ContentProvider implements Closeable {
 
     public static final String TABLE_SYSTEM = "system";
     public static final String TABLE_SECURE = "secure";

server/src/main/java/com/genymobile/scrcpy/wrappers/StatusBarManager.java

@@ -7,7 +7,7 @@ import android.os.IInterface;
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
 
-public class StatusBarManager {
+public final class StatusBarManager {
 
     private final IInterface manager;
     private Method expandNotificationsPanelMethod;