Restructure: Fix make install and lint

Makefile

@@ -1,7 +1,7 @@
 install:
 	python -m pip install --upgrade pip &&\
-		pip install -r requirements-dev.txt &&\
-		pip install -r esgtools/requirements.txt &&\
+		pip install -r dev_requirements.txt &&\
+		pip install -r lambda_requirements.txt &&\
 		pip install -r tests/test_requirements.txt &&\
 		pip install -e . --use-pep517
 

esgtools/lambdas/get_assets.py

@@ -1,4 +1,3 @@
-import json
 from ast import literal_eval
 
 import numpy as np

tests/utils/test_date_utils.py

@@ -1,7 +1,4 @@
 import datetime
-import json
-
-import pandas as pd
 import pytest
 from pytz import timezone