qdoc: Remove test that disallowed macro without params

A findFunctionNode() tree search function was testing whether a matching
node was a macro without parameters and refusing to return it if it was.
This test is now removed. Even if the test was necessary in some strange
situation, this was the wrong place to do it.

Change-Id: I40b2293f5643d2d752c05e16f85782f57c0ccbf3
Reviewed-by: Topi Reiniö <topi.reinio@qt.io>