fix: fixed the frequency buttons to remain unselected at the start of the wave generator screen (#2449)

Author: AsCress

app/src/main/res/layout/wave_generator_wave_controls.xml

@@ -124,7 +124,7 @@
                 android:layout_height="@dimen/length_0dp"
                 android:layout_marginStart="@dimen/margin_btn"
                 android:layout_marginTop="@dimen/margin_btn"
-                android:background="@drawable/btn_back_rounded"
+                android:background="@drawable/btn_back_rounded_light"
                 android:stateListAnimator="@animator/selector_animator"
                 android:text="@string/text_freq"
                 android:textAllCaps="false"
@@ -345,7 +345,7 @@
                 android:layout_height="0dp"
                 android:layout_marginStart="@dimen/margin_btn"
                 android:layout_marginTop="@dimen/margin_btn"
-                android:background="@drawable/btn_back_rounded"
+                android:background="@drawable/btn_back_rounded_light"
                 android:stateListAnimator="@animator/selector_animator"
                 android:text="@string/text_freq"
                 android:textAllCaps="false"