Remove requirement for Click>=8

[tunetheweb]

Brief summary of the change made

Fixes #2543

Not sure if this it the best way of doing this in Python, and don't think we can add test cases, so feel free to suggest improvements

Are there any other side effects of this change that we should be aware of?

Shouldn't be

Pull Request checklist

• Please confirm you have completed any of the necessary steps below.

• Included test cases to demonstrate any code changes, which may be one or more of the following:

  • .yml rule test cases in test/fixtures/rules/std_rule_cases.
  • .sql/.yml parser test cases in test/fixtures/dialects (note YML files can be auto generated with tox -e generate-fixture-yml).
  • Full autofix test cases in test/fixtures/linter/autofix.
  • Other.

• Added appropriate documentation for the change.

• Created GitHub issues for any relevant followup/future enhancements if appropriate.

[codecov]

Codecov Report

Merging #2547 (8d77369) into main (0102303) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main     #2547   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          163       163           
  Lines        11768     11771    +3     
=========================================
+ Hits         11768     11771    +3     

Impacted Files	Coverage Δ
src/sqlfluff/cli/autocomplete.py	100.00% <100.00%> (ø)
src/sqlfluff/cli/commands.py	100.00% <100.00%> (ø)

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[tunetheweb]

The alternative is we could just remove the dialect completion code. It's only a small thing, and that way we could just depend on the default completion for commands (which doesn't require ANY code on our side) and have people just have to type the dialect in full (shock! horror!).

WDYT?

[terzieff]

Hey,

so I just tried to use SQLFluff for the first time, installed it and got hit with this right away when doing sqlfluff version (happens with whatever method though):

Traceback (most recent call last):
  File "/opt/conda/bin/sqlfluff", line 5, in <module>
    from sqlfluff.cli.commands import cli
  File "/opt/conda/lib/python3.9/site-packages/sqlfluff/cli/commands.py", line 415, in <module>
    type=click.Choice([ft.value for ft in FormatType], case_sensitive=False),
TypeError: __init__() got an unexpected keyword argument 'case_sensitive'

It looks like I have click==6.7 and the issue looks similar to this and this. So maybe it'd make sense to require a certain version of click?