scripts/depscan: remove unnecessary function

This basically existed for an assert which we don't need, as mypy would
catch that issue for us anyway. Removing the function entirely has some
small performance advantages

mesonbuild/scripts/depscan.py

@@ -107,11 +107,6 @@ def scan_cpp_file(self, fname: str) -> None:
                 self.provided_by[exported_module] = fname
                 self.exports[fname] = exported_module
 
-    def objname_for(self, src: str) -> str:
-        objname = self.target_data.source2object[src]
-        assert isinstance(objname, str)
-        return objname
-
     def module_name_for(self, src: str, lang: Literal['cpp', 'fortran']) -> str:
         if lang == 'fortran':
             exported = self.exports[src]
@@ -131,7 +126,7 @@ def scan(self) -> int:
         with open(self.outfile, 'w', encoding='utf-8') as ofile:
             ofile.write('ninja_dyndep_version = 1\n')
             for src, lang in self.sources:
-                objfilename = self.objname_for(src)
+                objfilename = self.target_data.source2object[src]
                 mods_and_submods_needed = []
                 module_files_generated = []
                 module_files_needed = []