using correct namespace for THEXT class

Author: andreagilardoni

examples/sha256/sha256.ino

@@ -23,11 +23,11 @@ void setup() {
     sha256.update(buffer, sizeof(buffer));
     sha256.finalize(sha);
 
-    Serial.println(THEXT::encode(sha, sizeof(sha)));
+    Serial.println(hex::THEXT::encode(sha, sizeof(sha)));
 
     /* One-shot */
     SHA256::sha256(buffer, sizeof(buffer), sha);
-    Serial.println(THEXT::encode(sha, sizeof(sha)));
+    Serial.println(hex::THEXT::encode(sha, sizeof(sha)));
 }
 
 void loop() { }