[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

.github/workflows/schedule_nightly_test_a2.yaml

@@ -66,7 +66,6 @@ jobs:
             tests: tests/e2e/nightly/single_node/ops/multicard_ops_a2/
     uses: ./.github/workflows/_e2e_nightly_single_node.yaml
     with:
-      vllm: v0.14.1
       runner: ${{ matrix.test_config.os }}
       tests: ${{ matrix.test_config.tests }}
       name: ${{ matrix.test_config.name }}

.github/workflows/schedule_nightly_test_a3.yaml

@@ -161,7 +161,6 @@ jobs:
             tests: tests/e2e/nightly/single_node/models/test_deepseek_v3_2_w8a8.py
     uses: ./.github/workflows/_e2e_nightly_single_node.yaml
     with:
-      vllm: v0.14.1
       runner: ${{ matrix.test_config.os }}
       image: 'swr.cn-southwest-2.myhuaweicloud.com/base_image/ascend-ci/vllm-ascend:nightly-a3'
       tests: ${{ matrix.test_config.tests }}
@@ -181,7 +180,6 @@ jobs:
     uses: ./.github/workflows/_e2e_nightly_single_node.yaml
     with:
       runner: ${{ matrix.test_config.os }}
-      vllm: v0.14.1
       image: 'swr.cn-southwest-2.myhuaweicloud.com/base_image/ascend-ci/vllm-ascend:nightly-a3'
       tests: ${{ matrix.test_config.tests }}
       name: ${{ matrix.test_config.name }}