Fix include path in maliit-plugins.prf
Fix include path in maliit-plugins.prf

maliit-plugins depends on maliit-framework. Since maliit-framework is
headers only, just add the path to INCLUDEPATH.

RevBy: TrustMe

binlaten/framework,Elleo/framework,RHawkeyed/framework,Elleo/framework,RHawkeyed/framework,jpetersen/framework,jpetersen/framework