Do not pass class member "file_name" as argument

This is just unnecessary and not doing so avoids shadowing.

Author: tautschnig

src/cbmc/symex_coverage.cpp

@@ -91,7 +91,6 @@ class goto_program_coverage_recordt:public coverage_recordt
 
   void compute_coverage_lines(
     const goto_programt &goto_program,
-    const irep_idt &file_name,
     const symex_coveraget::coveraget &coverage,
     coverage_lines_mapt &dest);
 };
@@ -155,7 +154,6 @@ goto_program_coverage_recordt::goto_program_coverage_recordt(
   coverage_lines_mapt coverage_lines_map;
   compute_coverage_lines(
     gf_it->second.body,
-    file_name,
     coverage,
     coverage_lines_map);
 
@@ -220,7 +218,6 @@ goto_program_coverage_recordt::goto_program_coverage_recordt(
 
 void goto_program_coverage_recordt::compute_coverage_lines(
     const goto_programt &goto_program,
-    const irep_idt &file_name,
     const symex_coveraget::coveraget &coverage,
     coverage_lines_mapt &dest)
 {