Switch to javax.servlet:3.1.0

Implement new required methods for Servlet 3.1 in test classes:
  Servlet 3.1 introduces several new abstract methods on interfaces or
  classes that existed in servlet 2.5. Provide a mimimal, throwing
  implementation that largely allows servlet 2.5-written classes to
  compile and run using servlet 3.1.

PiperOrigin-RevId: 417877794
Change-Id: I9fe856fab678ede1b58dd7c0731bc5ed5927ed49

lib/jetty/BUILD

diff --git a/lib/jetty/BUILD b/lib/jetty/BUILD
index 521fd22..3a35ef5 100644
--- a/lib/jetty/BUILD
+++ b/lib/jetty/BUILD
@@ -8,7 +8,7 @@
     name = "servlet",
     exports = [
         ":security",
-        "//lib:servlet-api",  # Different from the rest of gitiles-server.
+        "//lib:servlet-api",
         "@servlet//jar",
     ],
 )