Ensure that js-plugins aren't cached (deephaven#4621)

This is an oversight discovered by web team and should have been part of deephaven#4389.

Added deephaven#4620 as eventual follow-up.

server/jetty/src/main/java/io/deephaven/server/jetty/JettyBackedGrpcServer.java

@@ -183,6 +183,8 @@ public JettyBackedGrpcServer(
         context.addFilter(new FilterHolder(filter), "/*", EnumSet.noneOf(DispatcherType.class));
 
         // Wire up /js-plugins/*
+        // TODO(deephaven-core#4620): Add js-plugins version-aware caching
+        context.addFilter(NoCacheFilter.class, JS_PLUGINS_PATH_SPEC, EnumSet.noneOf(DispatcherType.class));
         context.addServlet(servletHolder("js-plugins", jsPlugins.filesystem()), JS_PLUGINS_PATH_SPEC);
 
         // Set up websockets for grpc-web - depending on configuration, we can register both in case we encounter a