Meta: export "high water mark"

Used, e.g., in WebTransport.

index.bs

@@ -277,9 +277,9 @@ producer, but not yet processed and acknowledged by the [=underlying sink=].
 A <dfn>queuing strategy</dfn> is an object that determines how a stream should signal
 [=backpressure=] based on the state of its [=internal queue=]. The queuing strategy assigns a size
 to each [=chunk=], and compares the total size of all chunks in the queue to a specified number,
-known as the <dfn>high water mark</dfn>. The resulting difference, high water mark minus total size,
-is used to determine the <dfn lt="desired size to fill a stream's internal queue">desired size to
-fill the stream's queue</dfn>.
+known as the <dfn export>high water mark</dfn>. The resulting difference, high water mark minus
+total size, is used to determine the <dfn lt="desired size to fill a stream's internal
+queue">desired size to fill the stream's queue</dfn>.
 
 For readable streams, an underlying source can use this desired size as a backpressure signal,
 slowing down chunk generation so as to try to keep the desired size above or at zero. For writable