update requirements for research phase and exercise notebooks (#35)

exercise_notebooks/unit_testing_exercise/requirements.txt

@@ -1,4 +1,4 @@
-numpy>=1.18.1,<1.19.0
-scikit-learn>=0.22.1,<0.23.0
-pandas>=0.25.3,<0.26.0
+numpy>=1.20.0,<1.21.0
+pandas>=1.3.5,<1.4.0
+scikit-learn>=1.0.2,<1.1.0
 jupyter>=1.0.0,<1.1.0

research_phase/requirements.txt

@@ -1,6 +1,9 @@
-numpy>=1.18.1,<1.19.0
-scikit-learn>=0.22.1,<0.23.0
-pandas>=0.25.3,<0.26.0
+# We use compatible release functionality (see PEP 440 here: https://www.python.org/dev/peps/pep-0440/#compatible-release)
+# to specify acceptable version ranges of our project dependencies. This gives us the flexibility to keep up with small
+# updates/fixes, whilst ensuring we don't install a major update which could introduce backwards incompatible changes.
+numpy>=1.20.0,<1.21.0
+pandas>=1.3.5,<1.4.0
+scikit-learn>=1.0.2,<1.1.0
 jupyter>=1.0.0,<1.1.0
 feature_engine>=0.3.1,<0.4.0
-matplotlib>=3.1.2,<3.2.0
+matplotlib>=3.1.2,<4.0.0