fix: Dependabot recommendations

Author: jhrcook

requirements.txt

@@ -17,7 +17,7 @@ keras-preprocessing=1.1.01af3_0
 matplotlib
 nbconvert=5.6.1
 nbformat=5.0.4
-notebook=6.0.3
+notebook=6.1.5
 numpy=1.18.1
 opencv-python=4.2.0.32
 pandas=0.25.3
@@ -29,7 +29,7 @@ scipy=1.4.1
 seaborn=0.9.0
 statsmodels=0.11.1
 tensorboard=2.1.1
-tensorflow=2.1.0
+tensorflow>=2.4.0
 tensorflow-datasets=2.1.0
 tensorflow-estimator=2.1.0
 tensorflow-metadata=0.21.1