doc: Fix link to 'Installing Qt for Mac OS X' in the Mac section
doc: Fix link to 'Installing Qt for Mac OS X' in the Mac section

Change-Id: Idac663c78c4adf7a60b855d7cfaafa88f708bdc6
Reviewed-by: Jerome Pasion <c10995d24f6b454503389e8d00d837aef038985d@digia.com>

kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc,kobolabs/qtdoc