fix: bring memote back up to speed with recent cobra release

[ChristianLieven]

• fix Unpin Cobrapy Dependency and fix all associated errors #445
• Unpinned the Cobrapy dependency and updated memote's uses of model.exchanges to model.boundary where appropriate.
• add an entry to the next release

[ChristianLieven]

@Midnighter Do you think we could disable the tests relating to our syntax.py helper module? The functions there are deprecated and not used in any of the core tests.

[Midnighter]

Absolutely, I will make a quick PR to remove them. Didn't even realize that we're still lugging them around.

[Midnighter]

Done, so try again after rebasing.

[ChristianLieven]

This should not fail anymore once this fix to cobrapy is merged: opencobra/cobrapy#733

[codecov-io]

Codecov Report

Merging #470 into develop will not change coverage.
The diff coverage is 0%.

@@          Coverage Diff           @@
##           develop   #470   +/-   ##
======================================
  Coverage        0%     0%           
======================================
  Files           23     23           
  Lines         1159   1156    -3     
  Branches       252    248    -4     
======================================
+ Misses        1155   1152    -3     
  Partials         4      4

Impacted Files	Coverage Δ
memote/support/consistency_helpers.py	0% <0%> (ø)	⬆️
memote/support/consistency.py	0% <0%> (ø)	⬆️
memote/support/helpers.py	0% <0%> (ø)	⬆️

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