Make the pygments shortcode test matching less specific

So it does not fail on "other" pygments versions.

hugolib/shortcode_test.go

@@ -519,7 +519,7 @@ e`,
 		// #2223 pygments
 		{"sect/doc6.md", "\n```bash\nb: {{< b >}} c: {{% c %}}\n```\n",
 			filepath.FromSlash("sect/doc6/index.html"),
-			"<div class=\"highlight\"><pre><code class=\"language-bash\" data-lang=\"bash\"><span></span>b: b c: c\n</code></pre></div>\n"},
+			"b: b c: c\n</code></pre></div>\n"},
 		// #2249
 		{"sect/doc7.ad", `_Shortcodes:_ *b: {{< b >}} c: {{% c %}}*`,
 			filepath.FromSlash("sect/doc7/index.html"),
@@ -612,7 +612,7 @@ tags:
 
 		content := helpers.ReaderToString(file)
 
-		if content != test.expected {
+		if !strings.Contains(content, test.expected) {
 			t.Fatalf("%s content expected:\n%q\ngot:\n%q", test.outFile, test.expected, content)
 		}
 	}