baselineserver: Fix compilation by removing PI_BuildKey from the source

The buildkey support was removed in 7493ee1c44. This commit removed
PI_BuildKey and most of the usages from the code.

Change-Id: I971d68cd4377c358381983c1edcb98360936b698
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>

tests/baselineserver/src/baselineserver.cpp

@@ -532,7 +532,6 @@ void BaselineHandler::testPathMapping()
     item.itemChecksum = 0x0123;
 
     clientInfo.insert(PI_QtVersion, QLS("5.0.0"));
-    clientInfo.insert(PI_BuildKey, QLS("(nobuildkey)"));
     clientInfo.insert(PI_QMakeSpec, QLS("linux-g++"));
     clientInfo.insert(PI_PulseGitBranch, QLS("somebranch"));