[Build] Kill 3D code

src/Makefile.am

 bin_PROGRAMS = \
-	one-body-sample-2D \
-	one-body-sample-3D
-
-2d: one-body-sample-2D
-3d: one-body-sample-3D
+	one-body-sample-2D
 
 SOURCES = \
 	assemblers.cc \
@@ -21,12 +17,6 @@ one_body_sample_2D_SOURCES = $(SOURCES)
 one_body_sample_2D_CPPFLAGS = \
 	$(AM_CPPFLAGS) -Dsrcdir=\"$(abs_srcdir)\" -DDIM=2
 
-## 3D
-one_body_sample_3D_SOURCES = $(SOURCES)
-
-one_body_sample_3D_CPPFLAGS = \
-	$(AM_CPPFLAGS) -Dsrcdir=\"$(abs_srcdir)\" -DDIM=3
-
 # Some are for clang, others are for gcc
 AM_CXXFLAGS = \
 	-Wall \