prompt: Don't trim whitespace from prompts

New lines can be an important part of a user's prompt and trimming
it can alter the results. We previously only trimmed prompts with
images but refactoring brought this behavior to all prompts, where
it became more noticable.

The /generate endpoint adds less whitespace and therefore doesn't
need to trim it out - this brings the same behavior to /chat.

Thanks to @gabe-l-hart for spotting the issue!

Fixes #7795

server/prompt.go

@@ -114,7 +114,6 @@ func chatPrompt(ctx context.Context, m *Model, tokenize tokenizeFunc, opts *api.
 					ID:   len(images),
 					Data: i,
 				}
-				imgPrompt = " "
 			}
 
 			imgTag := fmt.Sprintf("[img-%d]", imgData.ID)
@@ -126,7 +125,7 @@ func chatPrompt(ctx context.Context, m *Model, tokenize tokenizeFunc, opts *api.
 
 			images = append(images, imgData)
 		}
-		msgs[currMsgIdx+cnt].Content = strings.TrimSpace(prefix + imgPrompt + prompt)
+		msgs[currMsgIdx+cnt].Content = prefix + imgPrompt + prompt
 	}
 
 	// truncate any messages that do not fit into the context window