Removed OpenMapSurfer

[joker234]

MapSurfer isn't available anymore. I tried to remove it properly. Please have a look if you need to change something else.

More information:

• remove OpenMapSurfer tile sources leaflet-extras/leaflet-providers#354 (comment)
• https://ask.openrouteservice.org/t/mapsurfer-discontinued/1873

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[joker234]

P.S.: if you want, you can discard/close this PR and update the tile sources from https://github.com/leaflet-extras/leaflet-providers instead.

[schloerke]

Closing in favor of #27

Thank you for your PR and patience