Some tests for the Null-aware elements language feature might need udpating

[chloestefantsova]

The following are suggested updates in the tests.

Duplicating keys in a map literal (given that e1 is a compile-time constant and is known to have the value 1) should be removed.

• co19/LanguageFeatures/Control-flow-collections/Null-aware-elements/constants_A01_t01.dart

  Lines 38 to 46 in c09143e

  	const map = {
  	?e1: 1,
  	e1: ?null,
  	e1: ?nil,
  	?e1: ?e2,
  	?null: e2,
  	?nil: e2,
  	1: ?e1
  	};

• co19/LanguageFeatures/Control-flow-collections/Null-aware-elements/constants_A01_t02.dart

  Lines 40 to 65 in c09143e

  	const {
  	?e1: 1,
  	// ^
  	// [analyzer] unspecified
  	// [cfe] unspecified
  	?1: 2,
  	// ^
  	// [analyzer] unspecified
  	// [cfe] unspecified
  	e1: ?1,
  	// ^
  	// [analyzer] unspecified
  	// [cfe] unspecified
  	1: ?e1,
  	// ^
  	// [analyzer] unspecified
  	// [cfe] unspecified
  	?e1: ?e2,
  	// ^
  	// [analyzer] unspecified
  	// [cfe] unspecified
  	?1: ?2
  	// ^
  	// [analyzer] unspecified
  	// [cfe] unspecified
  	};

Error message locations should be updated for the CFE.

• https://github.com/dart-lang/co19/blob/master/LanguageFeatures/Control-flow-collections/Null-aware-elements/disambiguating_A01_t02.dart
• https://github.com/dart-lang/co19/blob/master/LanguageFeatures/Control-flow-collections/Null-aware-elements/disambiguating_A02_t02.dart

Typos.

• (f4) should be replaced with f(4) in https://github.com/dart-lang/co19/blob/master/LanguageFeatures/Control-flow-collections/Null-aware-elements/runtime_A02_t02.dart
• Missing > and an extra ? in

  co19/LanguageFeatures/Control-flow-collections/Null-aware-elements/syntax_A01_t01.dart

  Line 76 in c09143e

  List<Map<String, int>? m = 2 > 1 ? ? [{"k": 0}] : null;