_config.yml: removed four merged notebooks from exclude list.

[dulude]

Relevant Ticket

• SPB-1766

Summary
The following notebooks were merged into main, and _toc.yml was updated to include them, but they were never removed from the exclude_list in _config.yml:

• wfc3_image_displayer_analyzer.ipynb (PR Add WFC3 notebook 'wfc3_image_displayer_analyzer.ipynb' #105)
• IR_IMA_Visualization_with_an_Example_of_Time_Variable_Background.ipynb (PR Add WFC3 notebook 'IR_IMA_Visualization_with_an_Example_of_Time_Variable_Background.ipynb' #106)
• phot_examples.ipynb (PR Add WFC3 notebook 'phot_examples.ipynb' #110)
• TVB_flattenramp_notebook.ipynb (PR Add WFC3 notebook 'TVB_flattenramp_notebook.ipynb' #111)

This PR simply removes the above notebooks from the exclude_list and fixes that oversight.