fixed typo in readme -- from colledges to colleges (#1108)

README.md

@@ -131,7 +131,7 @@ We appreciate all contributions to improve MMDetection. Please refer to [CONTRIB
 
 ## Acknowledgement
 
-MMDetection is an open source project that is contributed by researchers and engineers from various colledges and companies. We appreciate all the contributors who implement their methods or add new features, as well as users who give valuable feedbacks.
+MMDetection is an open source project that is contributed by researchers and engineers from various colleges and companies. We appreciate all the contributors who implement their methods or add new features, as well as users who give valuable feedbacks.
 We wish that the toolbox and benchmark could serve the growing research community by providing a flexible toolkit to reimplement existing methods and develop their own new detectors.