Rename the scripts that update the policy files

script/commit-current-upstream-policy-docs is now
script/write-upstream-policy-files: it writes the policy files and
commits nothing. script/update-policy is now
script/commit-upstream-policy-files, and make update-policy is now
make commit-upstream-policy-files. test/update-policy.sh follows.
Behaviour is unchanged.

Model: opus-5-5

Makefile

@@ -1,4 +1,4 @@
-.PHONY: bootstrap setup test lint fmt fmt-check check docker hooks commit-current-upstream-policy-docs update-policy
+.PHONY: bootstrap setup test lint fmt fmt-check check docker hooks write-upstream-policy-files commit-upstream-policy-files
 
 # Makefile targets are thin shims; the implementations live in script/
 # per the scripts-to-rule-them-all pattern (see the Entrypoints section
@@ -31,8 +31,8 @@ docker:
 hooks:
 	@script/install-precommit
 
-commit-current-upstream-policy-docs:
-	@script/commit-current-upstream-policy-docs
+write-upstream-policy-files:
+	@script/write-upstream-policy-files
 
-update-policy:
-	@script/update-policy
+commit-upstream-policy-files:
+	@script/commit-upstream-policy-files