[v14] build: Fix darwin product signing for legacy environments (#40741)

Fix the `DEVELOPER_ID_INSTALLER` environment variable for the old
`promote` and `build` environments for signing darwin packages. It was
accidentally set to the APPLICATION ID which made `productsign` break
when signing mac packages. The new `build-prod` and `build-stage`
environments are unaffected.

Exhibit-a: https://github.com/gravitational/teleport.e/actions/runs/8759563303/job/24044196635#step:11:42

darwin-signing.mk

@@ -60,7 +60,7 @@ TSH_SKELETON_build_prod = tsh
 
 TEAMID_promote = $(TEAMID_build_prod)
 DEVELOPER_KEY_NAME_promote = $(DEVELOPER_KEY_NAME_build_prod)
-INSTALLER_KEY_NAME_promote = $(DEVELOPER_KEY_NAME_build_prod)
+INSTALLER_KEY_NAME_promote = $(INSTALLER_KEY_NAME_build_prod)
 TELEPORT_BUNDLEID_promote = $(TELEPORT_BUNDLEID_build_prod)
 TSH_BUNDLEID_promote = $(TSH_BUNDLEID_build_prod)
 TSH_SKELETON_promote = $(TSH_SKELETON_build_prod)
@@ -75,7 +75,7 @@ TSH_SKELETON_build_stage = tshdev
 
 TEAMID_build = $(TEAMID_build_stage)
 DEVELOPER_KEY_NAME_build = $(DEVELOPER_KEY_NAME_build_stage)
-INSTALLER_KEY_NAME_build = $(DEVELOPER_KEY_NAME_build_stage)
+INSTALLER_KEY_NAME_build = $(INSTALLER_KEY_NAME_build_stage)
 TELEPORT_BUNDLEID_build = $(TELEPORT_BUNDLEID_build_stage)
 TSH_BUNDLEID_build = $(TSH_BUNDLEID_build_stage)
 TSH_SKELETON_build = $(TSH_SKELETON_build_stage)