LPC11U35_501 removed from uVision exporter targets

uvision4_lpc11u35_501.uvproj.tmpl is missing so the export fails.

I am removing this so that the option to export is removed.

https://github.com/mbedmicro/mbed/commit/147b4a41af3e237a425683bd5040f07254d45c4a in this commit the test, which would have shown this problem, was removed and the broken exporter was re-enabled having been disabled in https://github.com/mbedmicro/mbed/commit/a5794b11078965c644d78d770eb129c1097877cf