feat: Upgrade to Uploadcare API 0.7

Fixes #68.

Author: carlspring

src/main/java/com/uploadcare/api/RequestHelper.java

@@ -117,7 +117,7 @@ public void setApiHeaders(HttpUriRequest request, String requestBodyMD5) {
         String formattedDate = rfc2822(calendar.getTime());
 
         request.addHeader("Content-Type", JSON_CONTENT_TYPE);
-        request.setHeader("Accept", "application/vnd.uploadcare-v0.6+json");
+        request.setHeader("Accept", "application/vnd.uploadcare-v0.7+json");
         request.setHeader("Date", formattedDate);
         request.setHeader("User-Agent",
                 String.format("javauploadcare/%s/%s", LIBRARY_VERSION, client.getPublicKey()));