fix(ci): remove git reset command from Jenkinsfile

• By default, the variable eNB_CommitID is set as 'develop' in the config
• When OAI-FLEXRIC-RAN-Integration-Test is triggered by upstream FlexRIC push events, it takes develop
• Triggered by RAN takes commit SHA where origin/SHA does not work

Below are issues seen after this week's merge to develop:

• https://jenkins-oai.eurecom.fr/view/RAN/job/RAN-Ubuntu-ARM-Image-Builder/4103/pipeline-overview/?selected-node=44

08:43:07  + git reset --hard origin/9777d23173a740de7cf982659fae13ad6627d3aa
08:43:07  fatal: ambiguous argument 'origin/9777d23173a740de7cf982659fae13ad6627d3aa': unknown revision or path not in the working tree.

When triggered through upstream FlexRIC (as a PUSH Event), it is taking the branch as shown in the logs:

• https://jenkins-oai.eurecom.fr/job/OAI-FLEXRIC-RAN-Integration-Test/3832/pipeline-overview/?selected-node=47

13:45:27  + git reset --hard origin/develop
13:45:27  HEAD is now at 9777d23173 Merge branch 'integration_2026_w06' into 'develop'

Reverts changes done in -> !3895 (merged)