pin netCDF4=1.5.3 in min-all-deps (#4982)

Author: mathause

ci/requirements/py37-min-all-deps.yml

@@ -25,7 +25,9 @@ dependencies:
   - lxml=4.5  # Optional dep of pydap
   - matplotlib-base=3.1
   - nc-time-axis=1.2
-  - netcdf4=1.5
+# netcdf follows a 1.major.minor[.patch] convention (see https://github.com/Unidata/netcdf4-python/issues/1090)
+# bumping the netCDF4 version is currently blocked by #4491
+  - netcdf4=1.5.3
   - numba=0.48
   - numpy=1.17
   - pandas=1.0