Convert more DOM_NO_ERR cases to assertions

There is some risk to this change. The first is that I made a mistake. The
other is that one of the APIs that doesn't currently return an error changes
in the future.

src/server.zig

@@ -29,8 +29,6 @@ const log = @import("log.zig");
 const App = @import("app.zig").App;
 const CDP = @import("cdp/cdp.zig").CDP;
 
-const TimeoutCheck = std.time.ns_per_ms * 100;
-
 const MAX_HTTP_REQUEST_SIZE = 4096;
 
 // max message size