revert embedded templates to use prompt/response

This reverts commit 19753c18c0.

for compat. messages will be added at a later date

template/granite-instruct.gotmpl

@@ -1,16 +1,3 @@
-{{- if .Messages }}
-{{- if .System }}System:
-{{ .System }}
-
-{{ end }}
-{{- range .Messages }}
-{{- if eq .Role "user" }}Question:
-{{- else if eq .Role "assistant" }}Answer:
-{{- end }}
-{{ .Content }}
-
-{{ end }}Answer:
-{{ else -}}
 {{ if .System }}System:
 {{ .System }}
 
@@ -20,4 +7,3 @@
 {{ end }}Answer:
 {{ .Response }}
 
-{{ end -}}