Only document "press repeatedly"

See the discussion on #10649.

Now that we have an animation describing "press repeatedly", the risk
and complexity of "press-and-hold" is not worth it anymore.

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

@@ -72,32 +72,12 @@ following screenshot is an example of such boot menu:</p>
   identified in step 3.</p>
 
   <ul>
-    <li>
-      <p>If a boot menu with a list of devices appears, select your USB stick
-    and press <span class="keycap">Enter</span>.</p>
-    </li>
+    <li>If a boot menu with a list of devices appears, select your USB stick
+     and press <span class="keycap">Enter</span>.</li>
 
-    <li>
-      <p>If the computer starts on another operating system, then:</p>
-
-      <ol>
-        <li><p>Shut down the computer.</p></li>
-
-        <li><p>Press-and-hold the potential boot menu key identified in step 3.</p></li>
-
-        <li><p>Switch on the computer again while holding the potential boot menu key pressed.</p>
-
-          <ul>
-            <p>If a boot menu with a list of devices appears, select your USB stick
-             and press <span class="keycap">Enter</span>.</p>
-
-            <p>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.</p>
-          </ul>
-        </li>
-      </ol>
-    </li>
+    <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>
   </ul>
 
   <p>If none of the potential boot menu keys identified in step 3 work or if