Remove `count` from artifacts page

What does this MR do and why?

🎏 This page is behind the artifacts_management_page feature flag

What: This MR removes code that used the count field from the artifacts GraphQL query; the pagination will now rely on hasPrevPage/hasNextPage instead.

Why: We cannot count the artifacts efficiently without adding a new index to to the ci_builds database table, which we are not ready/willing to do right now, so the count field was removed in !110626 (merged)

Screenshots or screen recordings

before: pagination does not appear	with this MR: pagination appears and works
Screen_Recording_2023-03-06_at_14.00.14	Screen_Recording_2023-03-06_at_13.58.07

How to set up and validate locally

1. git checkout mfluharty-remove-file-count-from-artifacts-page
2. echo "Feature.enable(:artifacts_management_page)" | bundle exec rails console to enable the feature flag
3. find/make a project that generates artifacts

you can use this CI yaml to generate some sample artifacts to manage:

# .gitlab-ci.yml

potato:
  stage: build
  script:
    - echo 'potato' >> potato.txt
  artifacts:
    expose_as: 'potato'
    paths: ['potato.txt']

tomato:
  stage: build
  script:
    - echo 'tomato' >> tomato.txt
  artifacts:
    expose_as: 'tomato'
    paths: ['tomato.txt']

pineapple:
  stage: build
  script:
    - echo 'pineapple' >> pineapple.txt
  artifacts:
    expose_as: 'pineapple'
    paths: ['pineapple.txt']

apple:
  stage: build
  script:
    - echo 'apple' >> apple.txt
  artifacts:
    expose_as: 'apple'
    paths: ['apple.txt']

toblerone:
  stage: build
  script:
    - echo 'toblerone' >> toblerone.txt
  artifacts:
    expose_as: 'toblerone'
    paths: ['toblerone.txt']

4. run enough pipelines to have >20 jobs with artifacts OR set JOBS_PER_PAGE to a number less than the number of jobs with artifacts
5. make sure the pagination works

to run tests

6. bundle exec rspec spec/frontend/fixtures/job_artifacts.rb to generate the fixture
7. yarn install && yarn jest spec/frontend/artifacts/components/job_artifacts_table_spec.js

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.