cameracalibrate: Fix build error on Mac OSX

It fails to build only on Mac OSX with the following error.

In file included from ../subprojects/gst-plugins-bad/ext/opencv/gstopencv.cpp:45:
../subprojects/gst-plugins-bad/ext/opencv/gstcameracalibrate.h:96:38: error: a space is required between consecutive right angle brackets (use '> >')
  std::vector<std::vector<cv::Point2f>> imagePoints;
                                     ^~
                                     > >
1 error generated.

Fix: #817
2 jobs for fix/817 in 4 minutes and 57 seconds (queued for 29 seconds)