text-name is an expression so flat string is okay - tweak issue297 to actually be invalid since text-face-name is not currently an expression

test/errorhandling/issue297.mss

@@ -1,4 +1,4 @@
 #t {
-  text-name: invalid;
-  text-face-name: "Dejagnu";
+  text-name: valid;
+  text-face-name: 2;
 }

test/errorhandling/issue297.result

@@ -1 +1 @@
-issue297.mss:2:2 Invalid value for text-name, the type expression is expected. invalid (of type keyword)  was given.
+issue297.mss:3:2 Invalid value for text-face-name, the type font is expected. 2 (of type float)  was given.