Fix SQLAlchemy version to v1.4.27, as v1.4.28

[robintw]

🧰 Issue

Fixes #1112.

🚀 Overview:

SQLAlchemy v1.4.28 emits more warnings in various situations (see here. These warnings are triggered by various geoalchemy functions we use. In our CI, we have it set to turn warnings into errors - which is a good idea in general, but means that we can get unexpected errors from dependencies being upgraded by minor point releases which change warnings rules.

The requirement for SQLAlchemy just required v1.4.x, which is normally ok as breaking changes shouldn't occur in a point release - but this doesn't apply to warnings. So, this PR fixes the version to v1.4.27.

There is already a PR in geoalchemy2 to fix these warnings, so once that PR is merged and a new version is released, then we can stop fixing the point version.

🤔 Reason:

Fix CI.

🔨Work carried out:

• Fix version of SQLAlchemy
• Tests pass

Confirmations

• I have chosen reviewers for my PR.
• I have chosen an appropriate label for the PR, adding interactive_review if reviewers will need to see UI
• I have extended/updated the documentation in \docs folder
• Any database content changes (Create, Edit, Delete) are recorded in the Log/Changes tables
• Any database schema changes are implemented via alembic revision transitions
• I have completed the mandatory sections of this document.
• I have deleted any unused sections.

📝 Developer Notes:

[codecov]

Codecov Report

Merging #1114 (5e16209) into develop (f006e5e) will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #1114      +/-   ##
===========================================
+ Coverage    80.06%   80.07%   +0.01%     
===========================================
  Files          110      110              
  Lines        11896    11896              
===========================================
+ Hits          9524     9526       +2     
+ Misses        2372     2370       -2     

Impacted Files	Coverage Δ
pepys_import/resolvers/command_line_resolver.py	94.85% <0.00%> (+0.25%)	⬆️
pepys_import/file/file_processor.py	98.73% <0.00%> (+0.31%)	⬆️

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