Resolve "Inconsistent schema - tmp_index_ci_pipelines_lock_version index"

What does this MR do and why?

In this MR, we are removing the following index (if exists):

• tmp_index_ci_pipelines_lock_version

up:

== 20220109133006 RemoveCiPipelinesLockVersionIndex: migrating ================
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:ci_pipelines, :id, {:where=>"lock_version IS NULL", :name=>"tmp_index_ci_pipelines_lock_version", :algorithm=>:concurrently})
   -> 0.0074s
-- remove_index(:ci_pipelines, {:where=>"lock_version IS NULL", :name=>"tmp_index_ci_pipelines_lock_version", :algorithm=>:concurrently, :column=>:id})
   -> 0.0076s
== 20220109133006 RemoveCiPipelinesLockVersionIndex: migrated (0.0163s) =======

down:

== 20220109133006 RemoveCiPipelinesLockVersionIndex: reverting ================
-- transaction_open?()
   -> 0.0000s
-- index_exists?(:ci_pipelines, :id, {:where=>"lock_version IS NULL", :name=>"tmp_index_ci_pipelines_lock_version", :algorithm=>:concurrently})
   -> 0.0086s
-- execute("SET statement_timeout TO 0")
   -> 0.0005s
-- add_index(:ci_pipelines, :id, {:where=>"lock_version IS NULL", :name=>"tmp_index_ci_pipelines_lock_version", :algorithm=>:concurrently})
   -> 0.0024s
-- execute("RESET statement_timeout")
   -> 0.0005s
== 20220109133006 RemoveCiPipelinesLockVersionIndex: reverted (0.0137s) =======

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Related to #349549 (closed)