Revert "coq-modules: add default to fix eval"

This reverts commit e20b65156cee92d30b43f8e339bd686bd83538cb.

pkgs/development/coq-modules/QuickChick/default.nix

···
       propagatedBuildInputs = [ coq-ext-lib simple-io ];
     };
   };
-  param = params."${coq.coq-version}" or params."8.8";
+  param = params."${coq.coq-version}";
 in
 
 stdenv.mkDerivation rec {

pkgs/development/coq-modules/Velisarios/default.nix

···
       sha256 = "0l9885nxy0n955fj1gnijlxl55lyxiv9yjfmz8hmfrn9hl8vv1m2";
     };
   };
-  param = params."${coq.coq-version}" or params."8.8";
+  param = params."${coq.coq-version}";
 in
 
 stdenv.mkDerivation rec {

pkgs/development/coq-modules/category-theory/default.nix

···
     "8.7" = v20180709;
     "8.8" = v20181016;
   };
-  param = params."${coq.coq-version}" or params."8.8";
+  param = params."${coq.coq-version}";
 in
 
 stdenv.mkDerivation rec {

pkgs/development/coq-modules/coq-haskell/default.nix

···
       sha256 = "09dq1vvshhlhgjccrhqgbhnq2hrys15xryfszqq11rzpgvl2zgdv";
     };
   };
-  param = params."${coq.coq-version}" or params."8.8";
+  param = params."${coq.coq-version}";
 in
 
 stdenv.mkDerivation rec {

pkgs/development/coq-modules/coqprime/default.nix

···
     "8.8" = v_8_8;
     "8.9" = v_8_8;
     };
-  param = params."${coq.coq-version}" or params."8.9"
+  param = params."${coq.coq-version}"
 ; in
 
 stdenv.mkDerivation rec {

pkgs/development/coq-modules/dpdgraph/default.nix

···
     sha256 = "0qvar8gfbrcs9fmvkph5asqz4l5fi63caykx3bsn8zf0xllkwv0n";
   };
 };
-param = params."${coq.coq-version}" or params."8.8";
+param = params."${coq.coq-version}";
 in
 
 stdenv.mkDerivation {

pkgs/development/coq-modules/equations/default.nix

···
       sha256 = "1sj7vyarmvp1w5kvbhgpgap1yd0yrj4n1jrla0wv70k0jrq5hhpz";
     };
   };
-  param = params."${coq.coq-version}" or params."8.8";
+  param = params."${coq.coq-version}";
 in
 
 stdenv.mkDerivation rec {