Pin pyproj to version 3.3.x in Docker image

[kbevers]

For some reason pyproj 3.4.0 from pypi does not apply grids in transformations to and from DVR90 (and probable also other cases).

This fixes the issue temporarily.

Demonstration using currently deployed API (v.1.2.1)

curl https://api.dataforsyningen.dk/rest/webproj_test/v1.2/trans/EPSG:4258/EPSG:7416/55.0,12.0,100?token=<token>
{"v1": 691875.6321396608, "v2": 6098907.825005012, "v3": 100.0, "v4": null}

v3 should not be the same in input and output.

[coveralls]

Pull Request Test Coverage Report for Build 3676978127

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 95.148%

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Totals
Change from base Build 3328236843:	0.0%
Covered Lines:	353
Relevant Lines:	371

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💛 - Coveralls