tests: Fix yang if-feature enum test

The original idea was that enum_ doesn't have a deafult constructor, so
I use lambda to assign a value to it. Lambdas are cool and all, but
SECTION doesn't work inside a lambda like that. Found via code coverage.

Change-Id: I363040ad894bb2fc537b6f3dc9f543ead2501d71
diff --git a/tests/yang.cpp b/tests/yang.cpp
index 9419051..dd7a031 100644
--- a/tests/yang.cpp
+++ b/tests/yang.cpp
@@ -688,18 +688,16 @@
                 node.first = "example-schema";
                 node.second = "activePort";
 
-                yang::Enum enums = [&ys]() {
-                    SECTION("weird ports disabled")
-                    {
-                        return createEnum({"utf2", "utf3"});
-                    }
-                    SECTION("weird ports enabled")
-                    {
-                        ys.enableFeature("example-schema", "weirdPortNames");
-                        return createEnum({"WEIRD", "utf2", "utf3"});
-                    }
-                    __builtin_unreachable();
-                }();
+                yang::Enum enums({});
+                SECTION("weird ports disabled")
+                {
+                    enums = createEnum({"utf2", "utf3"});
+                }
+                SECTION("weird ports enabled")
+                {
+                    ys.enableFeature("example-schema", "weirdPortNames");
+                    enums = createEnum({"WEIRD", "utf2", "utf3"});
+                }
 
                 type = yang::Union{{
                     yang::TypeInfo{createEnum({"wlan0", "wlan1"})},