util: remove unnecessary trim/trimLeft/trimRight wrappers

When needed, use boost::algorithm::trim/trim_left/trim_right directly.

Change-Id: I854d89e553c70ab20679a38922cec306fc57824d
Refs: #3006
diff --git a/src/util/string-helper.cpp b/src/util/string-helper.cpp
index 44083b3..4a4808f 100644
--- a/src/util/string-helper.cpp
+++ b/src/util/string-helper.cpp
@@ -20,14 +20,13 @@
  */
 
 #include "string-helper.hpp"
+#include "../encoding/buffer.hpp"
 #include "../encoding/buffer-stream.hpp"
 #include "../security/transform/buffer-source.hpp"
 #include "../security/transform/hex-decode.hpp"
 #include "../security/transform/hex-encode.hpp"
 #include "../security/transform/stream-sink.hpp"
 
-#include <boost/algorithm/string/trim.hpp>
-
 #include <sstream>
 #include <iomanip>
 
@@ -109,24 +108,6 @@
   return os.buf();
 }
 
-void
-trimLeft(std::string& str)
-{
-  boost::algorithm::trim_left(str);
-}
-
-void
-trimRight(std::string& str)
-{
-  boost::algorithm::trim_right(str);
-}
-
-void
-trim(std::string& str)
-{
-  boost::algorithm::trim(str);
-}
-
 std::string
 unescape(const std::string& str)
 {