Revert "[flang] Treat pre-processed input as fixed (#117563)"

This reverts commit 81d82ca.

Author: inaki-amatria

clang/lib/Driver/ToolChains/Flang.cpp

@@ -815,13 +815,6 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
 
   addFortranDialectOptions(Args, CmdArgs);
 
-  // 'flang -E' always produces output that is suitable for use as fixed form
-  // Fortran. However it is only valid free form source if the original is also
-  // free form.
-  if (InputType == types::TY_PP_Fortran &&
-      !Args.getLastArg(options::OPT_ffixed_form, options::OPT_ffree_form))
-    CmdArgs.push_back("-ffixed-form");
-
   handleColorDiagnosticsArgs(D, Args, CmdArgs);
 
   // LTO mode is parsed by the Clang driver library.