Typo in stm32l0_dfu_bootloader.bat breaks download "with bootloader"

[terrillmoore]

Yikes. There's a typo in stm32l0-upload.bat -- I did final test on macOS and Linux but evidently didn't come back to Windows.

Arduino_Core_STM32/tools/windows/stm32l0-upload.bat

Line 122 in b24c769

"%.\dfu-util.exe" -d %VIDPID%0x0483:0xdf11 -a 0 -s 0x08000000 -D "%bootloader%"

The %.\dfu-util.exe is wrong, should be .\dfu-util.exe.

Only affects download "with bootloader".