remove `REACT_APP_CONFIG` from `.env` #7709

Job	Run time
Test	3m 17s
Build & Push Staging to container registries	0s
Build & Push Production to container registries	0s
Deploy to GKE Manipur	0s
Deploy to GKE Sikkim	0s
Deploy to GKE Karnataka	0s
Deploy to GKE Assam	0s
Deploy to GKE Nagaland	0s
	3m 17s

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