Change lack of content-type to be a permanent failure

In practice, I see this happening on URLs with unknown filetypes

quickpeep_raker/src/raking.rs

@@ -331,9 +331,8 @@ impl Raker {
             content_type.split(";").next().unwrap().trim().to_owned()
         } else {
             increment_counter!("qprake_rake_specific_fail_count", "reason" => "NoCT");
-            return Ok(RakeOutcome::TemporaryFailure(TemporaryFailure {
-                reason: TemporaryFailureReason::MissingInformation("content-type".to_owned()),
-                backoff_sec: 86400 * 7,
+            return Ok(RakeOutcome::PermanentFailure(PermanentFailure {
+                reason: PermanentFailureReason::UnknownContentType("not specified".to_owned()),
             }));
         };