Increase citation delay prompt timeout to 15 seconds

By prompting after 3 seconds we catch a lot of people who click through
the prompt without bothering to read or figure out what it does and then
come to the forums report the citing "bugs". An increased timeout will
catch less people and those who are caught are possibly more likely to
figure out how delayed citing updates work since they would greatly
benefit from it.

chrome/content/zotero/xpcom/integration.js

@@ -51,7 +51,7 @@ const INTEGRATION_TYPE_ITEM = 1;
 const INTEGRATION_TYPE_BIBLIOGRAPHY = 2;
 const INTEGRATION_TYPE_TEMP = 3;
 
-const DELAY_CITATIONS_PROMPT_TIMEOUT = 3/*seconds*/;
+const DELAY_CITATIONS_PROMPT_TIMEOUT = 15/*seconds*/;
 const DELAYED_CITATION_STYLING = "\\uldash";
 const DELAYED_CITATION_STYLING_CLEAR = "\\ulclear";