refactor: Remove redundant c_str() calls in formatting

Our formatter, tinyformat, *never* needs `c_str()` for strings.
Remove redundant `c_str()` calls for:

- `strprintf`
- `LogPrintf`
- `tfm::format`

src/noui.cpp

@@ -45,7 +45,7 @@ bool noui_ThreadSafeMessageBox(const std::string& message, const std::string& ca
     if (!fSecure) {
         LogPrintf("%s%s\n", strCaption, message);
     }
-    tfm::format(std::cerr, "%s%s\n", strCaption.c_str(), message.c_str());
+    tfm::format(std::cerr, "%s%s\n", strCaption, message);
     return false;
 }
 
@@ -96,4 +96,4 @@ void noui_reconnect()
     noui_ThreadSafeQuestionConn.disconnect();
     noui_InitMessageConn.disconnect();
     noui_connect();
-}
+}