http: Display gzipped log files in the browser.

This is a follow-up of 2280ae18eb. The gzipped
log files are supposed to be displayed directly in the browser and not
downloaded. Set "Content-Disposition" header to "inline" to ensure that.

* src/cuirass/http.scm (respond-gzipped-file): Set to "Content-Disposition" to
"inline".

src/cuirass/http.scm

@@ -272,7 +272,7 @@ Hydra format."
     ;; Return FILE with 'gzip' content-encoding.
     (respond `((content-type . (text/plain (charset . "UTF-8")))
                (content-encoding . (gzip))
-               (content-disposition . (form-data (filename . ,file)))
+               (content-disposition . (inline))
                (x-raw-file . ,file))))
 
   (define (respond-build-not-found build-id)