Include column alias in G-3182

[PhilippSalvisberg]

When reading G-3182 one could get the impression that column aliases cannot be referenced in the group by clause.

Therefore, change title from

G-3182: Always specify column names instead of positional references in GROUP BY clauses.

to

G-3182: Always specify column names/aliases instead of positional references in GROUP BY clauses.

and change the reason accordingly.

[PhilippSalvisberg]

closed via PR #215