Update process.rst

bring in @mattstauffer's changes to the text.

Author: matthewtrask

components/process.rst

@@ -377,10 +377,9 @@ instead::
 Using a Prepared Command Line
 -----------------------------
 
-You can run the process by using a a prepared command line using the
-double quotation notation. You can use a placeholder in order to have a
-process that can only be changed with the values and without changing
-the PHP code::
+You can run a process by using a prepared command line with double quote variable notation. 
+This allows you to use placeholders so that only the parameterized values can be changed, 
+but not the rest of the script:
 
     use Symfony\Component\Process\Process;