[Macros] Fix odd test case

The implementation was previously finding the wrong macro declaration,
leading to incorrect results recorded as the expected results.

Author: DougGregor

test/IDE/complete_macro_declaration.swift

@@ -7,7 +7,7 @@ macro expect(file: Int = #^DEFAULT_ARG^#) = #externalMacro(module: "MyModule", t
 // DEFAULT_ARG: Decl[GlobalVar]/CurrModule/TypeRelation[Convertible]: globalVar[#Int#]; name=globalVar
 
 @freestanding(expression)
-macro externalMacro() = ##^EXTERNAL_MACRO^#
+macro otherExternalMacro() = ##^EXTERNAL_MACRO^#
 // EXTERNAL_MACRO: Decl[Macro]/OtherModule[Swift]/IsSystem: externalMacro({#module: String#}, {#type: String#})[#T#]; name=externalMacro(module:type:)
 
 @freestanding(expression)