fix: syst_langu does not exist on older releases (#6999)

Co-authored-by: Marc Bernard <[email protected]>

Author: AndreaBorgia-Abo

abaplint.json

@@ -207,6 +207,7 @@
         "^sychar70$",
         "^sydatum$",
         "^sylangu$",
+        "^syst_langu$",
         "^syst_title$",
         "^syuzeit$",
         "^xubname$"

src/objects/zcl_abapgit_object_intf.clas.locals_imp.abap

@@ -707,7 +707,7 @@ CLASS lcl_aff_metadata_handler IMPLEMENTATION.
           ls_aff_data         TYPE zif_abapgit_aff_intf_v1=>ty_main,
           lo_type_mapper      TYPE REF TO zif_abapgit_aff_type_mapping,
           ls_ag_data          TYPE zcl_abapgit_object_intf=>ty_intf,
-          lv_sap1             TYPE syst_langu.
+          lv_sap1             TYPE sy-langu.
 
     lt_translation_file = io_files->read_i18n_files( ).