ci: allow MPL-2.0

Signed-off-by: Christina Sørensen <christina@cafkafk.com>

deny.toml

@@ -100,6 +100,7 @@ allow = [
   "MIT",
   "Unicode-DFS-2016",
   "Apache-2.0",
+  "MPL-2.0",
   #"Apache-2.0 WITH LLVM-exception",
 ]
 # The confidence threshold for detecting a license from license text.