fix: record each platform's own list version

install/<platform>.json wrote the constant "1.0" as the version of the
list it was built from. The manifest now carries the version the platform
YAML records, and generate_pack refuses a YAML without one.

inherits: no longer passes a parent's version to a child: Lakka was
published as RetroArch v1.22.2 in its manifest, pack name and site page.
lakka.yml records v6.1, the Lakka-LibreELEC tag its target list is read
at. The MiSTer scraper refuses a BiosDB without a timestamp instead of
writing an empty version.

A pack's manifest.json records list_version, so an install from the pack
alone knows it too. Manifests regenerated twice and compared: only
version and generated changed.

platforms/lakka.yml

@@ -1,5 +1,7 @@
 inherits: retroarch
 platform: Lakka
 homepage: "https://www.lakka.tv"
-# Version is inherited from retroarch.yml (fetched dynamically by scraper)
+# Lakka-LibreELEC's release tag, the revision platforms/targets/lakka.yml
+# reads its cores at. A version is never inherited from retroarch.yml.
+version: v6.1
 # Lakka uses the same BIOS requirements as RetroArch