Doc: Fix snippet showing -extensions usage for lupdate

Task-number: QTBUG-127352
Pick-to: 6.7
Change-Id: I5bb2e49b0b90da9c50b1eee00d77b9533e5379bb
Reviewed-by: Leena Miettinen <[email protected]>
(cherry picked from commit a0b6f24)
Reviewed-by: Qt Cherry-pick Bot <[email protected]>

Author: kkoehne

src/linguist/linguist/doc/src/linguist-manual.qdoc

@@ -412,10 +412,11 @@
     lupdate application.qrc -ts myapp_en.ts
     \endcode
 
-    To process all QML files without using a \c .qrc file:
+    To process all QML files in the current working directory (or its subfolders)
+    without using a \c .qrc file:
 
     \badcode
-    lupdate -extensions qml -ts myapp_en.ts
+    lupdate . -extensions qml -ts myapp_en.ts
     \endcode
 
     To check for translatable strings in both QML and C++ source files: