Move migration test fixtures to the correct directories (#21901)

Unfortunately #21549 changed the name of Testcases without changing
their associated fixture directories.

Fix #21854

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/migrations/fixtures/Test_UpdateOpenMilestoneCounts/expected_milestone.yml

@@ -0,0 +1,19 @@
+# type Milestone struct {
+#   ID              int64                  `xorm:"pk autoincr"`
+#   IsClosed        bool
+#   NumIssues       int
+#   NumClosedIssues int
+#   Completeness    int  // Percentage(1-100).
+# }
+-
+  id: 1
+  is_closed: false
+  num_issues: 3
+  num_closed_issues: 1
+  completeness: 33
+-
+  id: 2
+  is_closed: true
+  num_issues: 5
+  num_closed_issues: 5
+  completeness: 100

models/migrations/fixtures/Test_UpdateOpenMilestoneCounts/issue.yml

@@ -0,0 +1,25 @@
+# type Issue struct {
+#   ID               int64 `xorm:"pk autoincr"`
+#   RepoID           int64 `xorm:"INDEX UNIQUE(repo_index)"`
+#   Index            int64 `xorm:"UNIQUE(repo_index)"` // Index in one repository.
+#   MilestoneID      int64 `xorm:"INDEX"`
+#   IsClosed         bool  `xorm:"INDEX"`
+# }
+-
+  id: 1
+  repo_id: 1
+  index: 1
+  milestone_id: 1
+  is_closed: false
+-
+  id: 2
+  repo_id: 1
+  index: 2
+  milestone_id: 1
+  is_closed: true
+-
+  id: 4
+  repo_id: 1
+  index: 3
+  milestone_id: 1
+  is_closed: false

models/migrations/fixtures/Test_UpdateOpenMilestoneCounts/milestone.yml

@@ -0,0 +1,19 @@
+# type Milestone struct {
+#   ID              int64                  `xorm:"pk autoincr"`
+#   IsClosed        bool
+#   NumIssues       int
+#   NumClosedIssues int
+#   Completeness    int  // Percentage(1-100).
+# }
+-
+  id: 1
+  is_closed: false
+  num_issues: 4
+  num_closed_issues: 2
+  completeness: 50
+-
+  id: 2
+  is_closed: true
+  num_issues: 5
+  num_closed_issues: 5
+  completeness: 100