manually bump to 19.0.0 Alpha 03

manual bump because alpha automation failed to bump version because of
"Commits must have verified signatures".
See https://github.com/nextcloud/talk-android/pull/3733#issuecomment-2007183957

Signed-off-by: Marcel Hibbe <dev@mhibbe.de>

app/build.gradle

@@ -33,8 +33,8 @@ android {
 
         // mayor.minor.hotfix.increment (for increment: 01-50=Alpha / 51-89=RC / 90-99=stable)
         // xx   .xxx  .xx    .xx
-        versionCode 190000002
-        versionName "19.0.0 Alpha 02"
+        versionCode 190000003
+        versionName "19.0.0 Alpha 03"
 
         flavorDimensions "default"
         renderscriptTargetApi 19