fix ci for aslp_server. however...

the parent aslp repository seems to be aware of the child project
when executing `dune install`.
this leads to problems like

    $ dune install
    Error: The following <package>.install are missing:
    - _build/default/aslp_server/aslp_server.install
    Hint: try running 'dune build [-p <pkg>] @install'

running the suggested `dune build -p aslp_server @install`
will fail because asli is not installed yet.

so you have to

    dune build
    dune install -p asli
    dune build -p aslp_server @install
    dune install -p aslp_server

which is a bit uncomfortable

.github/workflows/opam.yml

@@ -30,6 +30,6 @@ jobs:
 
     - run: opam install . --deps-only --with-test
       working-directory: aslp_server
-    - run: opam exec -- dune build aslp_server --profile release
+    - run: opam exec -- dune build --profile release
       working-directory: aslp_server
 

aslp_server/aslp_server.opam

@@ -10,7 +10,7 @@ doc: "https://github.com/UQ-PAC/aslp"
 bug-reports: "https://github.com/UQ-PAC/aslp/issues"
 depends: [
   "ocaml"
-  "dune" {>= "3.16"}
+  "dune" {>= "2.8"}
   "cohttp-lwt-unix"
   "yojson"
   "asli"

aslp_server/bin/dune

@@ -1,5 +1,6 @@
 (executable
  (public_name aslp_server)
+ (modes exe byte)
  (name main)
  (modules main)
  (libraries asli.libASL lwt.unix yojson cohttp-lwt cohttp-lwt-unix pprint))

aslp_server/dune-project

@@ -1,4 +1,4 @@
-(lang dune 3.16)
+(lang dune 2.8)
 
 (name aslp_server)