update docs

docs/system-software.md

@@ -29,7 +29,7 @@ Then run:
 
     ./bin/first_time_macosx.sh
 
-On either Mac or Linux, when running a first-time setup, you'll be asked for your password.
+On either Mac or Linux, when running first-time setup, you'll be asked for your password.
 This is required for the setup script to perform various configurations (like installing packages,
 etc), some of which require the use of `sudo`.