Remove do_conf_str(encoding:)

It wasn't being used.

mesonbuild/utils/universal.py

@@ -1262,7 +1262,7 @@ def get_variable_regex(variable_format: Literal['meson', 'cmake', 'cmake@'] = 'm
 
 def do_conf_str(src: str, data: T.List[str], confdata: 'ConfigurationData',
                 variable_format: Literal['meson', 'cmake', 'cmake@'],
-                encoding: str = 'utf-8', subproject: T.Optional[SubProject] = None) -> T.Tuple[T.List[str], T.Set[str], bool]:
+                subproject: T.Optional[SubProject] = None) -> T.Tuple[T.List[str], T.Set[str], bool]:
     def line_is_valid(line: str, variable_format: str) -> bool:
         if variable_format == 'meson':
             if '#cmakedefine' in line:
@@ -1307,7 +1307,7 @@ def do_conf_file(src: str, dst: str, confdata: 'ConfigurationData',
     except Exception as e:
         raise MesonException(f'Could not read input file {src}: {e!s}')
 
-    (result, missing_variables, confdata_useless) = do_conf_str(src, data, confdata, variable_format, encoding, subproject)
+    (result, missing_variables, confdata_useless) = do_conf_str(src, data, confdata, variable_format, subproject)
     dst_tmp = dst + '~'
     try:
         with open(dst_tmp, 'w', encoding=encoding, newline='') as f: