lang/gcc8-devel: Remove

With the release of GCC 8.5 the GCC 8 release series has reached
end of life.

This also means the end of weekly snapshots. Remove lang/gcc8-devel
which has been tracking those and redirect to lang/gcc8 and that
final release instead.

MOVED

@@ -16386,3 +16386,4 @@ net/py-python-glanceclient2|net/py-python-glanceclient|2021-06-10|Remove obsolet
 net/py-python-keystoneclient3|net/py-python-keystoneclient|2021-06-10|Remove obsoleted port. Use net/py-python-keystoneclient instead
 net/py-python-novaclient16|net/py-python-novaclient|2021-06-10|Remove obsoleted port. Use net/py-python-novaclient instead
 print/py-pycups1|print/py-pycups|2021-06-10|Remove obsoleted port. Use print/py-pycups instead
+lang/gcc8-devel|lang/gcc8|2021-06-11|GCC 8 reached end of life, use the final release (or a new major version)

lang/Makefile

@@ -98,7 +98,6 @@
     SUBDIR += gcc6-aux
     SUBDIR += gcc7
     SUBDIR += gcc8
-    SUBDIR += gcc8-devel
     SUBDIR += gcc9
     SUBDIR += gcc9-devel
     SUBDIR += gforth