Codespell spelling fixes

These spelling errors were found using
https://github.com/codespell-project/codespell

Tested: Built and ran against validator.
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
Change-Id: I214fe102550295578cfdf0fc58305897d261ce55
diff --git a/http/utility.h b/http/utility.h
index 59abc8d..4792f6f 100644
--- a/http/utility.h
+++ b/http/utility.h
@@ -670,7 +670,7 @@
     output.reserve(((inputLength + 2) / 3) * 4);
 
     // for each 4-bytes sequence from the input, extract 4 6-bits sequences by
-    // droping first two bits
+    // dropping first two bits
     // and regenerate into 3 8-bits sequences
 
     for (size_t i = 0; i < inputLength; i++)