Fix a build failure due to PRs racing

swiftlang#1183 and swiftlang#1218 raced to create a build failure.

Author: ahoppen

Tests/SwiftSyntaxBuilderTest/FunctionTests.swift

@@ -152,7 +152,7 @@ final class FunctionTests: XCTestCase {
         """
       ),
       #line: (
-        FunctionDecl(
+        FunctionDeclSyntax(
           """
           public func foo(myOptionalValue: String?, myOtherOptionalValue: [String?])  {
           }

Tests/SwiftSyntaxBuilderTest/VariableTests.swift

@@ -48,43 +48,43 @@ final class VariableTests: XCTestCase {
         """
       ),
       #line: (
-        VariableDecl("var foo: String? { myOptional?.someProperty }"),
+        VariableDeclSyntax("var foo: String? { myOptional?.someProperty }"),
         """
         var foo: String? {
             myOptional?.someProperty
         }
         """
       ),
       #line: (
-        VariableDecl("let absoluteRaw = AbsoluteRawSyntax(raw: raw!, info: info)"),
+        VariableDeclSyntax("let absoluteRaw = AbsoluteRawSyntax(raw: raw!, info: info)"),
         """
         let absoluteRaw = AbsoluteRawSyntax(raw: raw!, info: info)
         """
       ),
       #line: (
-        VariableDecl("var foo: String { bar(baz!) }"),
+        VariableDeclSyntax("var foo: String { bar(baz!) }"),
         """
         var foo: String {
             bar(baz!)
         }
         """
       ),
       #line: (
-        VariableDecl(#"var foo: String { bar ?? "" }"#),
+        VariableDeclSyntax(#"var foo: String { bar ?? "" }"#),
         #"""
         var foo: String {
             bar ?? ""
         }
         """#
       ),
       #line: (
-        VariableDecl("let bar = try! (foo())"),
+        VariableDeclSyntax("let bar = try! (foo())"),
         """
         let bar = try! (foo())
         """
       ),
       #line: (
-        VariableDecl("let bar = try! !functionThatThrows()"),
+        VariableDeclSyntax("let bar = try! !functionThatThrows()"),
         """
         let bar = try! !functionThatThrows()
         """