Fix gluetun image tag: Docker Hub tags carry a v prefix

The issue plan listed qmcgaw/gluetun:3.41.1, but the published tag is
v3.41.1. appVersion is the exact image tag per the style guide, so
appVersion becomes v3.41.1 and the chart version 1.0.0+upv3.41.1
(precedent: matrix-synapse, satisfactory, calibre-web-automated).

freesailarr/Chart.yaml

@@ -5,8 +5,8 @@ icon: https://raw.githubusercontent.com/qdm12/gluetun/master/doc/logo_256.png
 
 type: application
 
-version: 1.0.0+up3.41.1
-appVersion: "3.41.1"
+version: 1.0.0+upv3.41.1
+appVersion: "v3.41.1"
 
 maintainers:
   - name: jklein