prover9: convert patchPhase to postPatch, cleanup meta

pkgs/applications/science/logic/prover9/default.nix

···
 
   hardeningDisable = [ "format" ];
 
-  patchPhase = ''
+  postPatch = ''
     RM=$(type -tp rm)
     MV=$(type -tp mv)
     CP=$(type -tp cp)
···
     cp bin/* $out/bin
   '';
 
-  meta = {
+  meta = with lib; {
     homepage = "https://www.cs.unm.edu/~mccune/mace4/";
-    license = "GPL";
+    license = license.gpl;
     description = "Automated theorem prover for first-order and equational logic";
     longDescription = ''
       Prover9 is a resolution/paramodulation automated theorem prover
       for first-order and equational logic. Prover9 is a successor of
       the Otter Prover. This is the LADR command-line version.
     '';
-    platforms = lib.platforms.linux;
-    maintainers = [ ];
+    platforms = platforms.linux;
+    maintainers = with maintainers; [ ];
   };
 }