Remove individual QMAKE_TARGET_PRODUCT's

It's been a while since we marketed either of the tools as separate
products. It's all "Qt5" now.

Change-Id: Id9ef7cfb217978039725d079da9a86043aed990a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

src/assistant/assistant/assistant.pro

@@ -102,7 +102,6 @@ FORMS += bookmarkdialog.ui \
 RESOURCES += assistant.qrc \
     assistant_images.qrc
 
-QMAKE_TARGET_PRODUCT = Qt Assistant
 QMAKE_TARGET_DESCRIPTION = Qt Assistant
 
 win32 {

src/designer/src/designer/designer.pro

@@ -59,7 +59,6 @@ FORMS += saveformastemplate.ui \
     preferencesdialog.ui \
     qdesigner_appearanceoptions.ui
 
-QMAKE_TARGET_PRODUCT = Qt Designer
 QMAKE_TARGET_DESCRIPTION = Qt Designer
 
 win32 {

src/linguist/linguist/linguist.pro

@@ -59,7 +59,6 @@ contains(QT_PRODUCT, OpenSource.*):DEFINES *= QT_OPENSOURCE
 DEFINES += QT_KEYWORDS
 TARGET = linguist
 
-QMAKE_TARGET_PRODUCT = Qt Linguist
 QMAKE_TARGET_DESCRIPTION = Qt Linguist
 
 win32 {