Remove un-used association

As this deployments association is now un-used, we can remove this.
It has the potential to create cross-db joins so let's remove it.

app/models/ci/pipeline.rb

@@ -72,7 +72,6 @@ module Ci
     has_many :build_trace_chunks, class_name: 'Ci::BuildTraceChunk', through: :builds, source: :trace_chunks
     has_many :trigger_requests, dependent: :destroy, foreign_key: :commit_id # rubocop:disable Cop/ActiveRecordDependent
     has_many :variables, class_name: 'Ci::PipelineVariable'
-    has_many :deployments, through: :builds
     has_many :latest_builds, -> { latest.with_project_and_metadata }, foreign_key: :commit_id, inverse_of: :pipeline, class_name: 'Ci::Build'
     has_many :downloadable_artifacts, -> do
       not_expired.or(where_exists(::Ci::Pipeline.artifacts_locked.where('ci_pipelines.id = ci_builds.commit_id'))).downloadable.with_job