Make date headers opaque.

Signed-off-by: Ivan Sein <ivan@nextcloud.com>

VideoCalls/DateHeaderView.xib

@@ -24,7 +24,7 @@
                 <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" fixedFrame="YES" text="Label" textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="PTc-Tu-Ciu">
                     <rect key="frame" x="135" y="5" width="90" height="24"/>
                     <autoresizingMask key="autoresizingMask" flexibleMinX="YES" flexibleMaxX="YES" flexibleMaxY="YES"/>
-                    <color key="backgroundColor" red="0.83529411764705885" green="0.83529411764705885" blue="0.83529411764705885" alpha="0.80000000000000004" colorSpace="calibratedRGB"/>
+                    <color key="backgroundColor" red="0.83529411764705885" green="0.83529411764705885" blue="0.83529411764705885" alpha="1" colorSpace="calibratedRGB"/>
                     <fontDescription key="fontDescription" type="system" pointSize="12"/>
                     <color key="textColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
                     <nil key="highlightedColor"/>