Update Kemal to 1.6.0 and remove Kilt

Kilt is unmaintained and the ECR templating logic has been
natively integrated into Kemal with the issues previously seen
having been resolved.

This commit is mostly a precursor to support the next Kemal
release which will add the ability to create error handlers for
raised exceptions.

See https://github.com/kemalcr/kemal/pull/688

shard.lock

@@ -18,7 +18,7 @@ shards:
 
   exception_page:
     git: https://github.com/crystal-loot/exception_page.git
-    version: 0.2.2
+    version: 0.4.1
 
   http_proxy:
     git: https://github.com/mamantoha/http_proxy.git
@@ -26,11 +26,7 @@ shards:
 
   kemal:
     git: https://github.com/kemalcr/kemal.git
-    version: 1.1.2
-
-  kilt:
-    git: https://github.com/jeromegn/kilt.git
-    version: 0.6.1
+    version: 1.6.0
 
   pg:
     git: https://github.com/will/crystal-pg.git