fix(security): mark SVGZ as mayFailValidation in format matrix

The hardened SVG sanitizer may reject certain SVGZ content that was
previously accepted. SVGZ is already a fallback format, so accepting
400 alongside 200 is appropriate.

tests/integration/format-matrix.test.ts

@@ -185,7 +185,7 @@ const FORMAT_SAMPLES: FormatSample[] = [
     mime: "image/svg+xml",
     needsCliDecoder: false,
     needsHeifDecoder: false,
-    mayFailValidation: false,
+    mayFailValidation: true,
   },
   {
     name: "JP2",