revert embedded templates to use prompt/response

This reverts commit 19753c18c0.

for compat. messages will be added at a later date

template/zephyr.gotmpl

@@ -1,15 +1,6 @@
-{{- if .Messages }}
-{{- if .System }}<|system|>
-{{ .System }}</s>
-{{ end }}
-{{- range .Messages }}<|{{ .Role }}|>
-{{ .Content }}</s>
-{{ end }}<|assistant|>
-{{ else -}}
 {{ if .System }}<|system|>
 {{ .System }}</s>
 {{ end }}{{ if .Prompt }}<|user|>
 {{ .Prompt }}</s>
 {{ end }}<|assistant|>
 {{ .Response }}</s>
-{{ end -}}