Update process.rst

Author: atailouloute

components/process.rst

@@ -146,7 +146,7 @@ operating system, you can write the above command as follows::
     $process = Process::fromShellCommandline('echo "${:MESSAGE}"');
 
 Portable commands require using a syntax that is specific to the component: when
-enclosing a variable name into ``"{$:`` and ``}"`` exactly, the process object
+enclosing a variable name into ``"${:`` and ``}"`` exactly, the process object
 will replace it with its escaped value, or will fail if the variable is not
 found in the list of environment variables attached to the command.