Made variables local in get_cols function

The variables blocks, blocks2, and cols were not set as local in the
get_cols function, which made neofetch print whatever value they had
before showing the colorblocks. This commit makes these variables local
so the output doesn't get affected if they are set beforehand.

neofetch

@@ -3359,6 +3359,7 @@ get_gpu_driver() {
 }
 
 get_cols() {
+    local blocks blocks2 cols
     if [[ "$color_blocks" == "on" ]]; then
         # Convert the width to space chars.
         printf -v block_width "%${block_width}s"