Revert "gemma4: add nothink renderer tests (#15554)" (#15555)

This reverts commit 1b70bb8a10.

model/renderers/gemma4_reference_test.go

@@ -704,13 +704,6 @@ func TestGemma4RendererMatchesReference(t *testing.T) {
 			think:    thinkTrue(),
 			expected: "<bos><|turn>system\n<|think|>\n<turn|>\n<|turn>user\nHi<turn|>\n<|turn>model\n",
 		},
-		{
-			name:       "nothink_no_system",
-			messages:   []api.Message{{Role: "user", Content: "Hi"}},
-			think:      thinkFalse(),
-			expected:   "<bos><|turn>user\nHi<turn|>\n<|turn>model\n",
-			skipJinja2: true,
-		},
 		{
 			name: "thinking_system",
 			messages: []api.Message{
@@ -1635,7 +1628,6 @@ func TestGemma4RendererKnownJinja2Differences(t *testing.T) {
 		name           string
 		messages       []api.Message
 		tools          []api.Tool
-		think          *api.ThinkValue
 		wantJinjaFrag  string
 		wantRenderFrag string
 	}{
@@ -1684,22 +1676,15 @@ func TestGemma4RendererKnownJinja2Differences(t *testing.T) {
 			wantJinjaFrag:  `response:read{value:<|"|>payload<|"|>}`,
 			wantRenderFrag: `response:unknown{value:<|"|>payload<|"|>}`,
 		},
-		{
-			name:           "explicit_nothink_skips_empty_thought_channel",
-			messages:       []api.Message{{Role: "user", Content: "Hi"}},
-			think:          thinkFalse(),
-			wantJinjaFrag:  "<|turn>model\n<|channel>thought\n<channel|>",
-			wantRenderFrag: "<|turn>model\n",
-		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
 			renderer := &Gemma4Renderer{useImgTags: RenderImgTags}
-			got, err := renderer.Render(tt.messages, tt.tools, tt.think)
+			got, err := renderer.Render(tt.messages, tt.tools, nil)
 			assert.NoError(t, err)
 
-			jinja2Output := renderWithJinja2(t, tt.messages, tt.tools, tt.think)
+			jinja2Output := renderWithJinja2(t, tt.messages, tt.tools, nil)
 			assert.NotEqual(t, jinja2Output, got, "case no longer differs from Jinja2 output")
 			assert.Contains(t, jinja2Output, tt.wantJinjaFrag)
 			assert.Contains(t, got, tt.wantRenderFrag)
@@ -1829,7 +1814,3 @@ print(tmpl.render(**kwargs), end="")
 func thinkTrue() *api.ThinkValue {
 	return &api.ThinkValue{Value: true}
 }
-
-func thinkFalse() *api.ThinkValue {
-	return &api.ThinkValue{Value: false}
-}