Revert "2025メンバーを追加、README更新"

[Art-Atlas]

Reverts #228

[github-actions]

Terraform Plan

Terraform used the selected providers to generate the following execution
plan. Resource actions are indicated with the following symbols:
  + create
  ~ update in-place
  - destroy

Terraform will perform the following actions:

  # github_membership.member["Nishinoyama"] will be destroyed
  # (because key ["Nishinoyama"] is not in for_each map)
  - resource "github_membership" "member" {
      - etag     = "W/\"44339cc580fd3ca1bc433cf3ccf3332af7345f0528ced4a794620caf657bdcc7\"" -> null
      - id       = "ictsc:Nishinoyama" -> null
      - role     = "admin" -> null
      - username = "Nishinoyama" -> null
    }

  # github_membership.member["nishinoyama"] will be created
  + resource "github_membership" "member" {
      + etag     = (known after apply)
      + id       = (known after apply)
      + role     = "admin"
      + username = "nishinoyama"
    }

  # github_membership.member["tosuke"] will be updated in-place
  ~ resource "github_membership" "member" {
        id       = "ictsc:tosuke"
      ~ role     = "member" -> "admin"
        # (2 unchanged attributes hidden)
    }

  # github_team_members.team_member["Admins"] will be updated in-place
  ~ resource "github_team_members" "team_member" {
        id      = "2008807"
        # (2 unchanged attributes hidden)

      + members {
          + role     = "maintainer"
          + username = "tosuke"
        }
      - members {
          - role     = "member" -> null
          - username = "tosuke" -> null
        }

        # (18 unchanged blocks hidden)
    }

  # github_team_members.team_member["ictsc2024"] will be updated in-place
  ~ resource "github_team_members" "team_member" {
        id      = "10324448"
        # (2 unchanged attributes hidden)

      - members {
          - role     = "maintainer" -> null
          - username = "takehaya" -> null
        }
      + members {
          + role     = "maintainer"
          + username = "tosuke"
        }
      - members {
          - role     = "member" -> null
          - username = "tosuke" -> null
        }

        # (27 unchanged blocks hidden)
    }

Plan: 1 to add, 3 to change, 1 to destroy.

─────────────────────────────────────────────────────────────────────────────

Note: You didn't use the -out option to save this plan, so Terraform can't
guarantee to take exactly these actions if you run "terraform apply" now.