fix don#t specify constexpr const values as std::string, but as const char*

Author: Totto16

src/lobby/api.cpp

@@ -14,7 +14,7 @@
 namespace {
     namespace constants {
 
-        constexpr const std::string api_token_key = "API_TOKEN_save";
+        constexpr const char* api_token_key = "API_TOKEN_save";
     }
 } // namespace
 

src/lobby/credentials/secret.cpp

@@ -10,7 +10,7 @@ namespace {
     namespace constants {
         constexpr const char* key_type_user = "user";
 
-        constexpr const std::string key_name_prefix = "OOPetris_key__";
+        constexpr const char* key_name_prefix = "OOPetris_key__";
     } // namespace constants
 
     std::string get_key_name(const std::string& key) {