Utils: Remove QtcProcess::{is,set}Synchronous

This reverts a bit of fe8fbf1a4a which was over-shooting API-wise.

Change-Id: Iac4c2b9fa550f7ec0b0aa8deea8c3fc6b6ddcfba
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/docker/dockerdevice.cpp

@@ -663,8 +663,8 @@ int DockerDevicePrivate::runSynchronously(const CommandLine &cmd) const
     QtcProcess proc;
     proc.setCommand(dcmd);
     proc.setWorkingDirectory("/tmp");
-    proc.setSynchronous(true);
     proc.start();
+    proc.waitForFinished();
 
     LOG("Run sync:" << dcmd.toUserOutput() << " result: " << proc.exitCode());
     return proc.exitCode();