Fix correct/incorrect example in "Templates - Names of Defined Templates"

[ILyaCyclone]

On Templates page https://helm.sh/docs/chart_best_practices/templates/#names-of-defined-templates in "Names of Defined Templates" section there is following text:

https://github.com/helm/helm-www/blob/7edf25def05c7d176c6aa818a615ae82ae451834/content/en/docs/chart_best_practices/templates.md?plain=1#L29-L45

This section describes necessity of using namespaces in variables names, so the key difference is "nginx.fullname" vs "fullname". But current and incorrect examples are also different in a dash symbol, added at the end of define in incorrect one: "{{- define "fullname" -}}".

I believe the only difference should be in naming: "nginx.fullname" vs "fullname".