Remove intro text from settings, fix button text color in dark mode

- Removed 'Sluit de ESP aan op USB en kies een actie.' from settings screen
- Button text now black on light gray background (readable in dark mode)

android/app/src/main/java/nl/eddydevink/sylda/MainActivity.kt

@@ -163,6 +163,7 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
         val b = ContextCompat.getColor(this, R.color.colorAccent)
         relay1Button.backgroundTintList = null
         relay1Button.setBackgroundColor(a)
+        relay1Button.setTextColor(Color.BLACK)
         relay1Button.setOnTouchListener { _, event ->
             when (event.action) {
                 MotionEvent.ACTION_DOWN -> {
@@ -187,6 +188,7 @@ class MainActivity : AppCompatActivity(), BleCallbacks {
         val b = ContextCompat.getColor(this, R.color.colorAccent)
         relay2Button.backgroundTintList = null
         relay2Button.setBackgroundColor(a)
+        relay2Button.setTextColor(Color.BLACK)
         relay2Button.setOnTouchListener { _, event ->
             when (event.action) {
                 MotionEvent.ACTION_DOWN -> {

android/app/src/main/res/layout/activity_settings.xml

@@ -5,13 +5,6 @@
     android:orientation="vertical"
     android:padding="24dp">
 
-    <TextView
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:text="@string/msg_settings_intro"
-        android:textSize="16sp"
-        android:layout_marginBottom="24dp" />
-
     <TextView
         android:layout_width="match_parent"
         android:layout_height="wrap_content"