Add a test-case for issue 6099 - CalRGB color space where the parameters are a |Ref|

The issue is already fixed by PR 5748, but we didn't have access to a suitable test-case. Thanks to issue 6099, we are now able to add one!

test/pdfs/.gitignore

@@ -89,6 +89,7 @@
 !issue5501.pdf
 !issue5599.pdf
 !issue5747.pdf
+!issue6099.pdf
 !gradientfill.pdf
 !bug903856.pdf
 !bug850854.pdf

test/test_manifest.json

@@ -1110,6 +1110,13 @@
        "link": false,
        "type": "eq"
     },
+    {  "id": "issue6099",
+       "file": "pdfs/issue6099.pdf",
+       "md5": "f8e9a26637c1b0d35f2bc653122a9c73",
+       "rounds": 1,
+       "link": false,
+       "type": "eq"
+    },
     {  "id": "bug893730",
        "file": "pdfs/bug893730.pdf",
        "md5": "2587379fb1b3bbff89c14f0863e78383",