Revert changes to symbols.map

Author: AlenkaF

cpp/src/arrow/symbols.map

@@ -34,7 +34,7 @@
     arrow_*;
     Arrow*;
     # ARROW-14771: export Protobuf symbol table
-    # descriptor_table_Flight*_2eproto;
+    descriptor_table_Flight*_2eproto;
 
   # Symbols marked as 'local' are not exported by the DSO and thus may not
   # be used by client applications.  Everything except the above falls here.