[Ada] Ada2020: parsing of qualified exprs with new agg syntax

[Ada] Ada2020: parsing of qualified exprs with new agg syntax

gcc/ada/

	* par-ch4.adb (P_Name): Allow Tok_Left_Bracket in two places to
	call P_Qualified_Expression. We don't need to modify other
	places that call P_Qualified_Expression, because a
	qualified_expression is a name in Ada 2012 and higher, so P_Name
	is the right place.  The parser already parses aggregates with
	brackets; we just need to allow that in qualified expressions.