Remove dead reference to ecpg resultmap file.

I missed this in my prior commit because it doesn't matter in non-VPATH
builds.

Per buildfarm.

Author: tglsfdc

src/interfaces/ecpg/test/Makefile

@@ -68,7 +68,7 @@ $(top_builddir)/src/port/pg_config_paths.h: $(top_builddir)/src/Makefile.global
 # $(srcdir) to the build directory.
 
 ifdef VPATH
-remaining_files_src := $(wildcard $(srcdir)/*/*.pgc) $(wildcard $(srcdir)/expected/*.c) $(wildcard $(srcdir)/expected/*.stdout) $(wildcard $(srcdir)/expected/*.stderr) $(srcdir)/resultmap
+remaining_files_src := $(wildcard $(srcdir)/*/*.pgc) $(wildcard $(srcdir)/expected/*.c) $(wildcard $(srcdir)/expected/*.stdout) $(wildcard $(srcdir)/expected/*.stderr)
 remaining_files_build := $(patsubst $(srcdir)/%, $(abs_builddir)/%, $(remaining_files_src))
 
 all: $(remaining_files_build)