fix(ci): remove specs tests

The https://github.com/hacspec/specs repository contains
specifications written in hacspec, mainly at the time of hacspec v1.

Since hacspec v1 is deprecated and archived, its library is deprecated
as well.

The hacspec lib (https://github.com/hacspec/hacspec/tree/master/lib)
doesn't typecheck any longer with `num-bigint` version `0.4.5`.

The hacspec lib dependents on `num-bigint` version `0.4`, not
specifying the minor version. The `specs` repository has no
`Cargo.lock`, and thus, from a clean `git clone`, `cargo build` pins
`num-bigint` to version `0.4.5`, breaking the hacspec library.

This broke #653 recently, and we
had the same kind of errors a couple times before in the past.

Two options were considered:
 - remove the tests related to the specs in the CI of hax;
 - commit a `Cargo.lock`.

The choose the first one: we need to update those specifications to
hax anyway: this will add motivation to
hacspec/specs#13.

.github/workflows/install_and_test.yml

@@ -41,33 +41,6 @@ jobs:
       with:
         repository: 'hacspec/specs'
         path: specs
-
-    - name: Extract specifications
-      working-directory: specs
-      run: |
-        paths=$(tomlq -r '.workspace.members | .[]' Cargo.toml)
-        for cratePath in $paths; do
-          crate=$(tomlq -r '.package.name' "$cratePath/Cargo.toml")
-          for backend in fstar coq; do
-            for skip in $SKIPLIST; do
-              if [[ "$skip" == "$crate" || "$skip" == "$crate-$backend" ]]; then
-                echo "⛔ $crate [$backend] (skipping)"
-                continue 2
-              fi
-            done
-            echo "::group::$crate [$backend]"
-            cargo hax -C -p "$crate" \; into "$backend"
-            echo "::endgroup::"
-          done
-        done
-      env:
-        SKIPLIST: |
-          tls_cryptolib
-          hacspec-merlin
-          hacspec-halo2-coq
-          hacspec-halo2-fstar
-          hacspec-weierstrass-coq
-          hacspec-weierstrass-fstar
 
     - name: Push to Cachix
       if: ${{ github.event_name == 'workflow_dispatch'  || github.event_name == 'merge_group'  }}