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

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

Added #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