Fix step numbers

wiki/src/install/inc/steps/pc_boot_menu.inline.html

@@ -69,7 +69,7 @@ following screenshot is an example of such boot menu:</p>
   <p>Switch on the computer.</p>
 
   <p>Immediately press several times the first potential boot menu key
-  identified in step 3.</p>
+  identified in step 2.</p>
 
   <ul>
     <li>If a boot menu with a list of devices appears, select your USB stick
@@ -77,10 +77,10 @@ following screenshot is an example of such boot menu:</p>
 
     <li>If the computer starts on another operating system or returns an
      error message, then shut down the computer again and repeat step
-     4 for all the potential boot menu keys identified in step 3.</li>
+     3 for all the potential boot menu keys identified in step 2.</li>
   </ul>
 
-  <p>If none of the potential boot menu keys identified in step 3 work or if
+  <p>If none of the potential boot menu keys identified in step 2 work or if
   the USB stick does not appear in the list, then try the second
   troubleshooting technique described below.</p>
 </li>