Don't remove version.m2 in "make clean"

Otherwise, subsequent calls to "make" will fail.

It's still removed by "make distclean"

[ci skip]

Author: d-torrance

M2/Macaulay2/m2/Makefile.in

@@ -24,7 +24,6 @@ DUMPEDM2DOCFILES := \
 ############################## version.m2
 all: version.m2
 version.m2: version.m2.in ; ./config.status Macaulay2/m2/version.m2
-clean::; rm -f version.m2
 ############################## tvalues.m2
 STOP = --stop
 ARGS = -q --silent $(STOP) -e errorDepth=0