minor #14005 [Process] Update process.rst (matthewtrask)

This PR was squashed before being merged into the 5.1 branch.

Discussion
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[Process] Update process.rst

This PR updates the text on the Process docs from "double brackets" which to a lot of people would mean `[[]]` to "double quotations" `""` as demonstrated in the code example for the prepared statement.

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Commits
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84de0dc [Process] Update process.rst

Author: javiereguiluz

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 bracket 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;