Remove non-functional command

This fails for two reasons
1) shell scripts run in their own instance, so this would be lost as
soon as the script finishes.
2) more importantly, this is Ubuntu, which has a short-circuit at the
top of the .bashrc to prevent it from running in a non-interactive shell

tools/setup_buildenv_ubuntu20.04.sh

@@ -82,7 +82,6 @@ fi
 
 echo "=== Step 9: Adding GNU Arm Embedded Toolchain to PATH of current user ==="
 echo 'export PATH="/opt/gcc-arm-none-eabi/bin:$PATH"' >> ~/.bashrc
-source ~/.bashrc
 if [[ $PAUSEAFTEREACHLINE == "true" ]]; then
   echo "Step finished. Please press Enter to continue or Ctrl+C to stop."
   read
@@ -127,4 +126,4 @@ if [[ $PAUSEAFTEREACHLINE == "true" ]]; then
   echo "Step finished."
 fi
 
-echo "Finished setting up EdgeTX v2.4 development environment. Please reboot the computer."
+echo "Finished setting up EdgeTX v2.4 development environment. Please reboot the computer."