tests: actually test printing of paths in unit test

This seems to be a copypasta mistake that slipped through when writing the
initial tests.  Changes the ValuePrintingTests::tPath to actually test a path
value instead of a string.

Change-Id: I20fe72635a0b1a6a0d72f674a4619da0de9f3d44

tests/unit/libexpr/value/print.cc

@@ -42,8 +42,8 @@ TEST_F(ValuePrintingTests, tString)
 TEST_F(ValuePrintingTests, tPath)
 {
     Value vPath;
-    vPath.mkString("/foo");
-    test(vPath, "\"/foo\"");
+    vPath.mkPath("/foo");
+    test(vPath, "/foo");
 }
 
 TEST_F(ValuePrintingTests, tNull)