[Nightly] Correct nightly image build ref (#6420)

### What this PR does / why we need it?
The underlying tags for nightly image builds have been corrected, and
some useless and confusing workflow fields have been removed.

- vLLM version: v0.14.1
- vLLM main:
dc917cceb8

Signed-off-by: wangli <wangli858794774@gmail.com>

.github/workflows/_e2e_nightly_single_node.yaml

@@ -20,9 +20,6 @@ name: 'e2e nightly test'
 on:
   workflow_call:
     inputs:
-      vllm:
-        required: true
-        type: string
       runner:
         required: true
         type: string