Revert "Pin base to workaround Format_doc change"

This reverts commit e2fa976.

The ocaml/ocaml#13336 PR restored backward compatibility for the
`Printtyp` module and the patch to `base` is no longer required.

Makefile

@@ -157,14 +157,6 @@ endif
 	opam pin add -n --yes --switch $* ocamlfind https://github.com/dra27/ocamlfind/archive/lib-layout.tar.gz
 	opam pin add -n --yes --switch $* coq-core https://github.com/ejgallego/coq/archive/refs/tags/multicore-2021-09-29.tar.gz
 	opam pin add -n --yes --switch $* coq-stdlib https://github.com/ejgallego/coq/archive/refs/tags/multicore-2021-09-29.tar.gz
-	# TODO remove when a new version of base is released on opam
-	# See https://github.com/ocaml-bench/sandmark/issues/470
-	@{ case "$*" in \
-		5.3.*) \
-			echo "Pinning base to fixed commit for Format_doc change"; \
-			opam pin add -n --yes --switch $* base.v0.17.0 https://github.com/ocaml-bench/base.git#fix-compat-format-doc;; \
-	    	*) echo "Nothing to do here" ;; \
-	esac };
 
 override_packages/%: setup_sys_dune/%
 	$(eval CONFIG_SWITCH_NAME = $*)