[Diagnostics] Update existential type error message for clarity

Author: mazevedofs

include/swift/AST/DiagnosticsSema.def

@@ -4758,7 +4758,7 @@ ERROR(unchecked_not_existential,none,
       "'unchecked' attribute cannot apply to non-protocol type %0", (Type))
 
 ERROR(redundant_any_in_existential,none,
-       "redundant 'any' has no effect on existential type %0",
+       "redundant 'any' in type 'any %0'",
        (Type))
 ERROR(any_not_existential,none,
        "'any' has no effect on %select{concrete type|type parameter}0 %1",

test/type/explicit_existential.swift

@@ -334,12 +334,12 @@ func testEnumAssociatedValue() {
 
 // https://github.com/apple/swift/issues/58920
 typealias Iterator = any IteratorProtocol
-var example: any Iterator = 5 // expected-error{{redundant 'any' has no effect on existential type 'Iterator' (aka 'any IteratorProtocol')}} {{14-18=}} 
+var example: any Iterator = 5 // expected-error{{redundant 'any' in type 'any 'Iterator' (aka 'any IteratorProtocol')'}} {{14-18=}}
 // expected-error@-1{{value of type 'Int' does not conform to specified type 'IteratorProtocol'}}
-var example1: any (any IteratorProtocol) = 5 // expected-error{{redundant 'any' has no effect on existential type 'any IteratorProtocol'}} {{15-19=}}
+var example1: any (any IteratorProtocol) = 5 // expected-error{{redundant 'any' in type 'any 'any IteratorProtocol''}} {{15-19=}}
 // expected-error@-1{{value of type 'Int' does not conform to specified type 'IteratorProtocol'}}
 
 protocol PP {}
 struct A : PP {}
 let _: any PP = A() // Ok
-let _: any (any PP) = A() // expected-error{{redundant 'any' has no effect on existential type 'any PP'}} {{8-12=}}
+let _: any (any PP) = A() // expected-error{{redundant 'any' in type 'any 'any PP''}} {{8-12=}}