fix licenCe typos

pkgs/tools/graphics/nifskope/default.nix

···
     description = "A tool for analyzing and editing NetImmerse/Gamebryo '*.nif' files";
     maintainers = [ stdenv.lib.maintainers.eelco ];
     platforms = stdenv.lib.platforms.linux;
-    licence = stdenv.lib.licenses.bsd3;
+    license = stdenv.lib.licenses.bsd3;
   };
 }

pkgs/tools/misc/tmpwatch/default.nix

···
     sha256 = "1m5859ngwx61l1i4s6fja2avf1hyv6w170by273w8nsin89825lk";
   };
 
-  meta = {
+  meta = with stdenv.lib; {
     homepage = https://fedorahosted.org/tmpwatch/;
     description = "The tmpwatch utility recursively searches through specified directories and removes files which have not been accessed in a specified period of time.";
-    licence = "GPLv2";
-    maintainers = with stdenv.lib.maintainers; [ vlstill ];
-    platforms = stdenv.lib.platforms.unix;
+    license = licenses.gpl2;
+    maintainers = with maintainers; [ vlstill ];
+    platforms = platforms.unix;
   };
 }