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/python2-modules/filelock/default.nix

@@ -15,7 +15,7 @@ buildPythonPackage rec {
 
   meta = with lib; {
     homepage = "https://github.com/benediktschmitt/py-filelock";
-    description = "A platform independent file lock for Python";
+    description = "Platform independent file lock for Python";
     license = licenses.unlicense;
     maintainers = with maintainers; [ henkkalkwater ];
   };

pkgs/development/python2-modules/hypothesis/default.nix

@@ -38,7 +38,7 @@ buildPythonPackage rec {
   '';
 
   meta = with lib; {
-    description = "A Python library for property based testing";
+    description = "Python library for property based testing";
     homepage = "https://github.com/HypothesisWorks/hypothesis";
     license = licenses.mpl20;
   };

pkgs/development/python2-modules/pyparsing/default.nix

@@ -37,7 +37,7 @@ let
 
     meta = with lib; {
       homepage = "https://github.com/pyparsing/pyparsing";
-      description = "An alternative approach to creating and executing simple grammars, vs. the traditional lex/yacc approach, or the use of regular expressions";
+      description = "Alternative approach to creating and executing simple grammars, vs. the traditional lex/yacc approach, or the use of regular expressions";
       license = licenses.mit;
     };
   };

pkgs/development/python2-modules/scandir/default.nix

@@ -16,7 +16,7 @@ buildPythonPackage rec {
   checkPhase = "${python.interpreter} test/run_tests.py";
 
   meta = with lib; {
-    description = "A better directory iterator and faster os.walk()";
+    description = "Better directory iterator and faster os.walk()";
     homepage = "https://github.com/benhoyt/scandir";
     license = licenses.gpl3;
     maintainers = with maintainers; [ abbradar ];

pkgs/development/python2-modules/wheel/default.nix

@@ -38,7 +38,7 @@ buildPythonPackage rec {
 
   meta = with lib; {
     homepage = "https://github.com/pypa/wheel";
-    description = "A built-package format for Python";
+    description = "Built-package format for Python";
     longDescription = ''
       This library is the reference implementation of the Python wheel packaging standard,
       as defined in PEP 427.