Remove the web-server exception handler

This turned out not to be useful, since I wanted to handle exceptions
happening in the exception handler, so it didn't really help in the
end to allow customising it.

tests/web-server.scm

@@ -52,28 +52,6 @@
         uri
         #:port (non-blocking-open-socket-for-uri uri)))))))
 
-(run-fibers-for-tests
- (lambda ()
-   (let* ((web-server
-           (run-knots-web-server
-            (lambda (request)
-              "Hello, World!")
-            #:port 0
-            #:exception-handler
-            (lambda (exn request)
-              "Error"))) ;; Bind to any port
-          (port
-           (web-server-port web-server))
-          (uri
-           (build-uri 'http #:host "127.0.0.1" #:port port)))
-
-     (assert-equal
-      500
-      (response-code
-       (http-get
-        uri
-        #:port (non-blocking-open-socket-for-uri uri)))))))
-
 (run-fibers-for-tests
  (lambda ()
    (let* ((web-server