Ensure consistent AggregatedReaction screenshots

Different system locales can generate different screenshots, causing CI
to be unhappy. Hardcoding a locale ensures the same date format is
always used.

Signed-off-by: Joe Groocock <me@frebib.net>

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/model/AggregatedReactionProvider.kt

@@ -38,10 +38,10 @@ fun anAggregatedReaction(
     count: Int = 1,
     isHighlighted: Boolean = false,
 ): AggregatedReaction {
+    val timeFormatter = DateFormat.getTimeInstance(DateFormat.SHORT, java.util.Locale.US)
+    val date = Date(1_689_061_264L)
     val senders = buildList {
         repeat(count) { index ->
-            val timeFormatter = DateFormat.getTimeInstance(DateFormat.SHORT)
-            val date = Date(1_689_061_264L)
             add(
                 AggregatedReactionSender(
                     senderId = if (isHighlighted && index == 0) userId else UserId("@user$index:server.org"),