treewide: Per RFC45, remove all unquoted URLs

pkgs/applications/science/robotics/apmplanner2/default.nix

@@ -46,7 +46,7 @@ mkDerivation rec {
       A GUI ground control station for autonomous vehicles using the MAVLink protocol.
       Includes support for the APM and PX4 based controllers.
     '';
-    homepage = https://ardupilot.org/planner2/;
+    homepage = "https://ardupilot.org/planner2/";
     license = lib.licenses.gpl3;
     maintainers = with lib.maintainers; [ wucke13 ];
   };

pkgs/applications/science/robotics/betaflight-configurator/default.nix

@@ -41,7 +41,7 @@ stdenv.mkDerivation rec {
       Various types of aircraft are supported by the tool and by Betaflight, e.g. 
       quadcopters, hexacopters, octocopters and fixed-wing aircraft.
     '';
-    homepage    = https://github.com/betaflight/betaflight/wiki;
+    homepage    = "https://github.com/betaflight/betaflight/wiki";
     license     = licenses.gpl3;
     maintainers = with maintainers; [ wucke13 ];
     platforms   = platforms.linux;

pkgs/applications/science/robotics/gazebo/default.nix

@@ -75,7 +75,7 @@ stdenv.mkDerivation rec {
     ++ optional withHdf5Support hdf5;
 
   meta = with stdenv.lib; {
-    homepage = http://gazebosim.org/;
+    homepage = "http://gazebosim.org/";
     description = "Multi-robot simulator for outdoor environments";
     license = licenses.asl20;
     maintainers = with maintainers; [ pxc ];

pkgs/applications/science/robotics/yarp/default.nix

@@ -28,7 +28,7 @@ stdenv.mkDerivation rec {
 
   meta = {
     description = "Yet Another Robot Platform";
-    homepage = http://yarp.it;
+    homepage = "http://yarp.it";
     license = stdenv.lib.licenses.lgpl21;
     platforms = stdenv.lib.platforms.linux;
     maintainers = [ stdenv.lib.maintainers.nico202 ];