L031 desc updated to cover both 'from' and 'join'

[nevado]

Brief summary of the change made

Small update to L031 description so it is clear that it covers both 'from' and 'join' clauses - previously was a bit confusing as it only mentioned 'join' clauses but will also trigger when there is no join present.

Fixes #1624

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

No

Pull Request checklist

All good

[tunetheweb]

@nevado you'll need to update this test case:

sqlfluff/test/cli/commands_test.py

Lines 49 to 53 in 0ebc703

	expected_output = """== [test/fixtures/linter/indentation_error_simple.sql] FAIL
	L: 2 | P: 4 | L003 | Indentation not hanging or a multiple of 4 spaces
	L: 5 | P: 10 | L010 | Keywords must be consistently upper case.
	L: 5 | P: 13 | L031 | Avoid using aliases in join condition
	"""

[codecov]

Codecov Report

Merging #1625 (6b2f536) into main (14e1a23) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main     #1625   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          131       131           
  Lines         9207      9207           
=========================================
  Hits          9207      9207           

Impacted Files	Coverage Δ
src/sqlfluff/rules/L031.py	100.00% <ø> (ø)

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