Fix link to MHV AVR Tools

keyboard/planck/PCB_GUIDE.md

@@ -3,7 +3,7 @@
 ## Setting up the environment
 
 ### Windows
-1. Install [MHV AVR Tools](https://github.com/jackhumbert/qmk_firmware). Disable smatch, but **be sure to leave the option to add the tools to the PATH checked**.
+1. Install [MHV AVR Tools](https://infernoembedded.com/sites/default/files/project/MHV_AVR_Tools_20131101.exe). Disable smatch, but **be sure to leave the option to add the tools to the PATH checked**.
 2. Install [MinGW](https://sourceforge.net/projects/mingw/files/Installer/mingw-get-setup.exe/download). During installation, uncheck the option to install a graphical user interface. **DO NOT change the default installation folder.** The scripts depend on the default location.
 3. Clone this repository. [This link will download it as a zip file, which you'll need to extract.](https://github.com/jackhumbert/qmk_firmware/archive/master.zip) Open the extracted folder in Windows Explorer.
 4. Right-click on the 1-setup-path-win batch script, select "Run as administrator", and accept the User Account Control prompt. Press the spacebar to dismiss the success message in the command prompt that pops up.