Fix typo (#18526)

docs/newbs_building_firmware.md

@@ -40,7 +40,7 @@ Open your `keymap.c` file in your text editor. Inside this file you'll find the
 
 This line indicates where the list of Layers begins. Below that you'll find lines containing `LAYOUT`, and these lines indicate the start of a layer. Below that line is the list of keys that comprise a particular layer.
 
-!> When editing your keymap file be careful not to add or remove any commas. If you do you will prevent your firmware from compiling and it may not be easy to figure out where the extra, or missing, comma is.
+!> When editing your keymap file be careful not to add or remove any commas. If you do, you will prevent your firmware from compiling and it may not be easy to figure out where the extra, or missing, comma is.
 
 ## Customize The Layout To Your Liking