[CI] [GHA] Fix a dependency conflict in the keras job by pinning of the recently updated dependencies (#33123)

### Details:
- Seems like the `grain` package that [was updated to 0.2.15 on the 25th
of November](https://pypi.org/project/grain/#history) is causing a
conflict in dependencies installation for the keras list of
dependencies.
I will create an issue in the keras repository later.

### Tickets:
 - *177685*

Author: akashchi

.github/workflows/job_keras3_backend.yml

@@ -91,7 +91,8 @@ jobs:
         working-directory: ${{ env.KERAS_REPO }}
         run: |
           pip install --upgrade pip setuptools
-          pip install -r requirements.txt --upgrade
+          # Specify grain's version to avoid problems described in the 177685 ticket
+          pip install -r requirements.txt grain==0.2.14 --upgrade
           pip install --no-deps tf_keras==2.18.0
           # make sure that no other keras is installed via pip
           pip uninstall -y keras keras-nightly

.github/workflows/ubuntu_22.yml

@@ -378,8 +378,7 @@ jobs:
 
   Keras3_OpenVINO_Backend:
     name: Keras 3 OpenVINO Backend Tests
-    # if: fromJSON(needs.smart_ci.outputs.affected_components).Python_API.test
-    if: ${{ 'false' }} # Ticket: 177685
+    if: fromJSON(needs.smart_ci.outputs.affected_components).Python_API.test
     needs: [ Docker, Build, Smart_CI, Openvino_tokenizers ]
     uses: ./.github/workflows/job_keras3_backend.yml
     with: