Make projects module available for custom import of CO-DETR

[bibekyess]

Motivation

I noticed that direct remote installation using pip install mmdet or mim install mmdet doesn't pull the projects module giving error like this:

>>> ImportError: Failed to import custom modules from {'allow_failed_imports': False, 'imports': ['projects.CO-DETR.codetr']}, the current sys.path is: 
...

In this PR, I made a small change so that the above issue will be resolved, without the need to either install git, clone the repo and install mmdet or remembering module_path to add it to system path.

Modification

The modification is very minor that it ensures complete backward-compatibility.

[CLAassistant]

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