build: adopt the snap version from Cargo.toml

The version: key in snapcraft.yaml was a second number to bump by
hand, and between releases it read whatever it was left at. The ecrou
part now sets its version from [workspace.package] at pull time —
the same value clap reports with --version — so Cargo.toml is the
only place a version lives, and the release workflow stamps only
that. A missed match fails the pack loudly.

.github/workflows/release.yml

@@ -51,8 +51,8 @@ jobs:
         run: |
           v="${GITHUB_REF_NAME#v}"
           sed -i "s/^version = \".*\"/version = \"$v\"/" Cargo.toml
-          sed -i "s/^version: \".*\"/version: \"$v\"/" snap/snapcraft.yaml
-          grep -H '^version' Cargo.toml snap/snapcraft.yaml
+          # The snap adopts this version from Cargo.toml at pull time.
+          grep -H '^version' Cargo.toml
 
       - uses: snapcore/action-build@v1
         id: build