CI: Fix the github actions Coverity run

The Install step is failing with:

  Package python-dev is not available, but is referred to by another package.
  This may mean that the package is missing, has been obsoleted, or
  E: Package 'python-dev' has no installation candidate
  is only available from another source
  However the following packages replace it:
    python2-dev python2 python-dev-is-python3

which is a side effect of ubuntu-latest having changed from 20.04 to 22.04.

Drop python-dev as python3-dev is already present, and used a fixed runs-on to
avoid such problems in the future.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

.github/workflows/coverity.yml

@@ -8,7 +8,7 @@ on:
 
 jobs:
   coverity:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     steps:
     - name: Install build dependencies
       run: |
@@ -18,7 +18,7 @@ jobs:
           libbz2-dev e2fslibs-dev uuid-dev ocaml \
           ocaml-findlib libyajl-dev \
           autoconf libtool liblzma-dev \
-          python3-dev golang python-dev libsystemd-dev
+          python3-dev golang libsystemd-dev
 
     - uses: actions/checkout@v2
       with: