Helm image tag updates dropping `v` on tags

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Package ecosystem

helm

### Package manager version

_No response_

### Language version

_No response_

### Manifest location and content before the Dependabot update

_No response_

### dependabot.yml content

``` yaml
version: 2
updates:
# Maintain dependencies for GitHub Actions
- package-ecosystem: "github-actions"
directory: "/"
schedule:
interval: "weekly"
commit-message:
prefix: "ci"
groups:
# group all minor/patch updates in one PR
version-updates:
dependency-type: production
applies-to: version-updates
update-types:
- "minor"
- "patch"
- package-ecosystem: "helm"
directories:
- "/charts/**/*"
schedule:
interval: "weekly"
commit-message:
prefix: "fix(deps)"
groups:
version-updates:
applies-to: version-updates
update-types:
- "minor"
- "patch"
```

### Updated dependency

The dependencies that have had this issue are:
- https://github.com/vllm-project/vllm v0.8.5 -> v0.9.0.1 & v0.9.0.1 -> v0.9.1
- https://github.com/llm-d/llm-d-inference-sim/pkgs/container/llm-d-inference-sim v0.1.1 -> v0.1.2

### What you expected to see, versus what you actually saw

Versions are updated to the correct tag, not missing the leading `v`. Some updates have correctly worked (first time llm-d-inference-sim was updated it was correctly updated), others result in the leading `v` in the tag being dropped. It also seems to be removing the newline at the end of the file when this happens.

### Native package manager behavior

_No response_

### Images of the diff or a link to the PR, issue, or logs

Example diff from PR:

### Smallest manifest that reproduces the issue

This should reproduce the issue in a values.yaml file for a chart.
``` yaml
test:
image:
repository: ghcr.io/llm-d/llm-d-inference-sim
tag: v0.1.1
```