pgmanage: use a valid version number

pkgs/applications/misc/pgmanage/default.nix

···
 { lib, stdenv, fetchFromGitHub, postgresql, openssl, nixosTests } :
-let
+stdenv.mkDerivation rec {
+  pname = "pgmanage";
   # The last release 11.0.1 from 2018 fails the NixOS test
   # probably because of PostgreSQL-12 incompatibility.
   # Fortunately the latest master does succeed the test.
-  rev = "a028604416be382d6d310bc68b4e7c3cd16020fb";
-in
-stdenv.mkDerivation rec {
-  pname = "pgmanage";
-  version = "11.0.1-git-${builtins.substring 0 7 rev}";
+  version = "unstable-2022-05-11";
 
   src = fetchFromGitHub {
     owner  = "pgManage";
     repo   = "pgManage";
-    inherit rev;
+    rev    = "a028604416be382d6d310bc68b4e7c3cd16020fb";
     sha256 = "sha256-ibCzZrqfbio1wBVFKB6S/wdRxnCc7s3IQdtI9txxhaM=";
   };