Fix output placeholders for icon_atmosphere_real.namelist

namelists/real-from-ideal/icon_atmosphere_real.namelist

@@ -42,8 +42,8 @@
 ! LATBC files
 &output_nml
     file_interval               = 'PT3600S'
-    output_start                = '%OUTPUT_START%'
-    output_end                  = '%OUTPUT_END%'
+    output_start                = '#OUTPUT_START#'
+    output_end                  = '#OUTPUT_END#'
     output_filename             = "latbc"
     output_interval             = 'PT3600S'
     include_last                = .true.