CI: Remove flake & mypy?

[adamcharnock]

Just throwing this out there for discussion. I love black, but using flake in addition just seems to throw up a bunch of noise that I don't think really makes much difference to code quality (it mostly just results in # noqa comments for me).

mypy is also being a bit of an irritant too. I did catch an error in a type annotation, but other than that it was (IMHO) just noise:

hordak/admin.py:51: error: "Callable[[AccountAdmin, Any], Any]" has no attribute "admin_order_field"  [attr-defined]
hordak/management/commands/create_benchmark_transactions.py:36: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
hordak/management/commands/create_benchmark_transactions.py:37: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
hordak/management/commands/create_benchmark_transactions.py:38: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
hordak/management/commands/create_benchmark_transactions.py:39: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
hordak/management/commands/create_benchmark_transactions.py:40: note: By default the bodies of untyped functions are not checked, consider using --check-untyped-defs  [annotation-unchecked]
hordak/management/commands/create_benchmark_transactions.py:82: error: Syntax error in type annotation  [syntax]
hordak/management/commands/create_benchmark_transactions.py:82: note: Suggestion: Use Tuple[T1, ..., Tn] instead of (T1, ..., Tn)
hordak/forms/transactions.py:178: error: Need type annotation for "source_account"  [var-annotated]
hordak/forms/transactions.py:182: error: Need type annotation for "trading_account"  [var-annotated]
hordak/forms/transactions.py:191: error: Need type annotation for "destination_account"  [var-annotated]
hordak/forms/statement_csv_import.py:13: error: Need type annotation for "bank_account"  [var-annotated]
hordak/views/transactions.py:65: error: Definition of "object" in base class "DeletionMixin" is incompatible with definition in base class "BaseDetailView"  [misc]

How helpful do other people find these two tools though?

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UPDATE: I'd also be happy to replace these with automatic tools such as (example). It isn't the changes I object to, rather it's the manual drudgery of having to follow rules that I'm not really sure I agree with.

[adamcharnock]

I've removed mypy as part of #127 (4a15aa1), because god help me.

Commit message:

Removing mypy. We're all consenting adults here. Let's catch these issues using our IDEs or in PR review. Black catches most of it anyway, #125