treewide: Remove indefinite article from meta.description

nix run nixpkgs#silver-searcher -- -G '\.nix$' -0l 'description.*"[Aa]n?' pkgs \
  | xargs -0 nix run nixpkgs#gnused -- -i '' -Ee 's/(description.*")[Aa]n? (.)/\1\U\2/'

pkgs/development/python-modules/cryptography/default.nix

@@ -92,7 +92,7 @@ buildPythonPackage rec {
   ];
 
   meta = with lib; {
-    description = "A package which provides cryptographic recipes and primitives";
+    description = "Package which provides cryptographic recipes and primitives";
     longDescription = ''
       Cryptography includes both high level recipes and low level interfaces to
       common cryptographic algorithms such as symmetric ciphers, message