fix: removed unnecessary function, update header file for signature change.

include/util/hex_checker.hpp

@@ -2,16 +2,9 @@
 
 #include <string>
 
-/**
- * Reads a CSS file, searches for 8-bit hex codes (#RRGGBBAA),
- * and returns true if found, or false if not found.
- */
-
-bool has_8bit_hex(std::string file_path);
-
 /**
  * Reads a CSS file, searches for 8-bit hex codes (#RRGGBBAA),
  * and transforms them into GTK-compatible rgba() syntax.
  */
 
-std::string transform_8bit_to_hex(std::string file_path);
+std::string transform_8bit_to_hex(const std::string& file_path);