Remove "in-daylight-saving-time" flag

This flag is problematic because when a time zone is "in DST" is not well
defined. Most time zones in the world don't use DST at all. Of the ones
that do, most go to DST during the summer for half the year, but not all.

For example, the function in Moment.js that provides this functionality
comes with a giant caveat:
https://momentjs.com/docs/#/query/is-daylight-saving-time/

Author: ptomato

wit-0.3.0-draft/timezone.wit

@@ -6,12 +6,11 @@ interface timezone {
     use system-clock.{instant};
 
     /// Return information needed to display the given `instant` in the
-    /// currently configured time zone. This includes the UTC offset, the time
-    /// zone name, and a flag indicating whether daylight saving time is active.
+    /// currently configured time zone. This includes the UTC offset and the
+    /// time zone name.
     ///
     /// If the currently configured timezone cannot be determined, return a
-    /// `timezone-display` for `UTC` with a `utc-offset` of 0 and no daylight
-    /// saving time.
+    /// `timezone-display` for `UTC` with a `utc-offset` of 0.
     @unstable(feature = clocks-timezone)
     display: func(when: instant) -> timezone-display;
 
@@ -21,9 +20,6 @@ interface timezone {
 
     /// Information useful for displaying a specific `instant` in the currently
     /// configured time zone.
-    ///
-    /// This information may vary within a single `timezone` to reflect daylight
-    /// saving time adjustments.
     @unstable(feature = clocks-timezone)
     record timezone-display {
         /// The number of seconds difference between UTC time and the local
@@ -46,11 +42,5 @@ interface timezone {
         /// In time zones that do not have an applicable name, a formatted
         /// representation of the UTC offset may be returned, such as `-04:00`.
         name: string,
-
-        /// Whether daylight saving time is active.
-        ///
-        /// In implementations that do not expose an actual time zone, this
-        /// should return false.
-        in-daylight-saving-time: bool,
     }
 }