src/scheduler: fix field name for storing k8s context name

[JenySadadia]

Correct field name for storing k8s cluster name to Node.data. Set data.job_context field to align with model definition.

Fixes: d916ba8 ("src/scheduler: store k8s context in the job node")

[JenySadadia]

Tested OK on staging:

$ curl https://staging.kernelci.org:9000/latest/node/65c4c8418cf2fd1548f0c087
{"id":"65c4c8418cf2fd1548f0c087","kind":"kbuild","name":"kbuild-gcc-10-arm64","path":["checkout","kbuild-gcc-10-arm64"],"group":"kbuild-gcc-10-arm64","parent":"65c4c7eb8cf2fd1548f0c086","state":"done","result":"fail","artifacts":{"build_log":"https://kciapistagingstorage1.file.core.windows.net/staging/kbuild-gcc-10-arm64-65c4c8418cf2fd1548f0c087/build.log?sv=2022-11-02&ss=f&srt=sco&sp=r&se=2024-10-17T19:19:12Z&st=2023-10-17T11:19:12Z&spr=https&sig=sLmFlvZHXRrZsSGubsDUIvTiv%2BtzgDq6vALfkrtWnv8%3D","metadata":"https://kciapistagingstorage1.file.core.windows.net/staging/kbuild-gcc-10-arm64-65c4c8418cf2fd1548f0c087/metadata.json?sv=2022-11-02&ss=f&srt=sco&sp=r&se=2024-10-17T19:19:12Z&st=2023-10-17T11:19:12Z&spr=https&sig=sLmFlvZHXRrZsSGubsDUIvTiv%2BtzgDq6vALfkrtWnv8%3D","fragments/0_config":"https://kciapistagingstorage1.file.core.windows.net/staging/kbuild-gcc-10-arm64-65c4c8418cf2fd1548f0c087/fragments/0.config?sv=2022-11-02&ss=f&srt=sco&sp=r&se=2024-10-17T19:19:12Z&st=2023-10-17T11:19:12Z&spr=https&sig=sLmFlvZHXRrZsSGubsDUIvTiv%2BtzgDq6vALfkrtWnv8%3D"},"data":{"kernel_revision":{"tree":"kernelci","url":"https://github.com/kernelci/linux.git","branch":"staging-stable","commit":"421ae7760cacaaa5f8dd652aea61ca0cac0820e8","describe":"staging-stable-20240208.1","version":{"version":"6","patchlevel":"1","sublevel":"77","extra":"-1-g421ae7760caca"}},"runtime":"k8s-all","platform":"kubernetes","job_id":"kci-65c4c8418cf2fd1548f0c087-kbuild-gcc-10-arm64-n1dewguc","job_context":"gke_android-kernelci-external_europe-west4-c_kci-eu-west4","arch":"arm64","compiler":"gcc-10","defconfig":"defconfig","fragments":[],"config_full":"defconfig"},"debug":null,"error_code":null,"created":"2024-02-08T12:25:37.416000","updated":"2024-02-08T12:59:19.686000","timeout":"2024-02-08T18:25:37.416000","holdoff":null,"owner":"staging.kernelci.org","user_groups":[]}