Update paperless-ngx to version 0.25.8

Bumped the paperless-ngx chart version from 0.25.7 to 0.25.8 in
Chart.yaml and updated the version badge in README.md to reflect
this change. The appVersion remains at 2.20.0.

Additionally, modified the type fields for readiness and liveness
probes in values.yaml from lowercase 'http' to uppercase 'HTTP'
for consistency and adherence to expected conventions. This change
ensures proper interpretation by Kubernetes. No breaking changes
have been introduced in this update.

charts/paperless-ngx/Chart.yaml

@@ -4,7 +4,7 @@ description: "A community-supported supercharged version of paperless: scan, ind
 home: https://charts.gabe565.com/charts/paperless-ngx/
 icon: https://raw.githubusercontent.com/paperless-ngx/paperless-ngx/b948750/src-ui/src/assets/logo-notext.svg
 type: application
-version: 0.25.7
+version: 0.25.8
 # renovate datasource=docker depName=ghcr.io/paperless-ngx/paperless-ngx
 appVersion: 2.20.0
 kubeVersion: ">=1.28.0-0"