Show event times in Berlin time

`toLocaleString()` was given the German locale but no time zone, so it printed
the time in whatever zone the browser of the visitor is set to. The events
happen in Berlin, so this is only correct for visitors who are in Berlin.
Somebody reading the start page from Sydney was told the Plenum of Tuesday
20:00 takes place on Wednesday at 04:00.

Format in Europe/Berlin explicitly. Only the printing was wrong, picking and
sorting the events works on absolute points in time and was not affected.

Drop the two replacements around the formatted date while touching it. The
first removes the comma after the weekday and the second puts it back, so they
cancel each other out:

  "Samstag, 22.08., 17:00" -> "Samstag 22.08., 17:00" -> "Samstag, 22.08., 17:00"

Fixes: c28f04c6e8 ("switch to ics files; make calendars work; fix some minor issues")
Assisted-by: Claude:claude-opus-5
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

static/js/upcoming.js

@@ -109,14 +109,17 @@ document.addEventListener("DOMContentLoaded", () => {
         const colBegin = document.createElement("td");
 
         const formattedStart = event.start.toLocaleString("de-DE", {
+          // The events take place in Berlin, so name their time in Berlin time
+          // instead of in the time zone the visitor happens to be in.
+          timeZone: "Europe/Berlin",
           weekday: "long",
           day: "2-digit",
           month: "2-digit",
           hour: "2-digit",
           minute: "2-digit",
-        }).replace(",", "");
+        });
 
-        colBegin.innerText = `${formattedStart.replace(" ", ", ")} Uhr`;
+        colBegin.innerText = `${formattedStart} Uhr`;
         row.appendChild(colBegin);
 
         const colName = document.createElement("td");