fix: using code blocks within release-notes

Increase the number of code blocks backticks to 4 for the release note prefix and suffix, to allow users to embed their own code blocks using only 3 backticks.

internal/testdata/description-overrides.txt

@@ -0,0 +1,44 @@
+<!-- section-start changelog -->
+## v1.0.0
+<!-- section-end changelog -->
+
+---
+
+<details>
+  <summary><h4>PR by <a href="https://github.com/apricote/releaser-pleaser">releaser-pleaser</a> 🤖</h4></summary>
+
+If you want to modify the proposed release, add you overrides here. You can learn more about the options in the docs.
+
+## Release Notes
+
+### Prefix / Start
+
+This will be added to the start of the release notes.
+
+~~~~rp-prefix
+## Foo
+
+- Cool thing
+
+```go
+// Some code example
+func IsPositive(number int) error {
+	if number < 0 {
+		return fmt.Errorf("number %d is negative", number)
+	}
+	return nil
+}
+```
+~~~~
+
+### Suffix / End
+
+This will be added to the end of the release notes.
+
+~~~~rp-suffix
+## Compatibility
+
+No compatibility guarantees.
+~~~~
+
+</details>