Update .qdoc files

examples/xlsx/documentproperty/doc/src/documentproperty.qdoc

@@ -4,7 +4,7 @@
     \title Xlsx DocProperties Example
     \brief This is a simplest xlsx examples.
 
-    \ingroup qtxlsx
+    \ingroup qtxlsx-examples
 
     This example demonstrates how to generate a
     .xlsx file with Qt Xlsx Library.

examples/xlsx/hello/doc/src/hello.qdoc

@@ -2,7 +2,7 @@
     \example hello
     \title Xlsx Hello Example
     \brief This is a simplest xlsx examples.
-    \ingroup qtxlsx
+    \ingroup qtxlsx-examples
 
     This example demonstrates how to generate a
     simplest .xlsx file with Qt Xlsx Library.

examples/xlsx/readwrite/doc/src/readwrite.qdoc

@@ -2,7 +2,7 @@
     \title Xlsx Readwrite Example
     \example readwrite
     \brief Open an existing xlsx file, modify and save it.
-    \ingroup qtxlsx
+    \ingroup qtxlsx-examples
 
     This example demonstrates how to modify an existing
     .xlsx file with Qt Xlsx Library.

examples/xlsx/style/doc/src/style.qdoc

@@ -3,8 +3,7 @@
     \example style
     \title Xlsx Style Example
     \brief This is a simplest xlsx examples.
-
-    \ingroup qtxlsx
+    \ingroup qtxlsx-examples
 
     This example demonstrates how to generate a
     .xlsx file with Qt Xlsx Library.