Fixed Spelling. (#1582)

diff --git a/src/ngx_base_fetch.cc b/src/ngx_base_fetch.cc
index 9ec3173..f880560 100644
--- a/src/ngx_base_fetch.cc
+++ b/src/ngx_base_fetch.cc
@@ -91,7 +91,7 @@
         NgxBaseFetch::active_base_fetches);
 
     // Try to continue processing and get the active base fetch count to 0
-    // untill the timeout expires.
+    // until the timeout expires.
     // TODO(oschaaf): This needs more work.
     while (NgxBaseFetch::active_base_fetches > 0 && end_us > timer.NowUs()) {
       event_connection->Drain();