.github: update the label for sigs (pingcap#19125)

Signed-off-by: shirly <[email protected]>

.github/labeler.yml

@@ -1,4 +1,4 @@
-component/executor:
+sig/executor:
   - distsql/*
   - executor/*
   - util/chunk/*
@@ -13,7 +13,7 @@ component/expression:
   - expression/*
   - types/*
 
-component/planner:
+sig/planner:
   - planner/*
   - bindinfo/*
   - util/ranger/*
@@ -22,7 +22,7 @@ component/planner:
 component/statistics:
   - statistics/*
 
-component/DDL:
+sig/DDL:
   - ddl/*
   - domain/*
   - infoschema/*

.github/workflows/assign_project.yml

@@ -15,15 +15,15 @@ jobs:
       uses: srggrs/[email protected]
       if: |
         contains(github.event.issue.labels.*.name, 'component/coprocessor') ||
-        contains(github.event.issue.labels.*.name, 'component/executor') ||
+        contains(github.event.issue.labels.*.name, 'sig/executor') ||
         contains(github.event.issue.labels.*.name, 'component/expression')
       with:
         project: 'https://github.com/pingcap/tidb/projects/38'
         column_name: 'Issue Backlog: Need Triage'
     - name: Run issues assignment to project SIG Planner Kanban
       uses: srggrs/[email protected]
       if: |
-        contains(github.event.issue.labels.*.name, 'component/planner') ||
+        contains(github.event.issue.labels.*.name, 'sig/planner') ||
         contains(github.event.issue.labels.*.name, 'component/statistics') ||
         contains(github.event.issue.labels.*.name, 'component/bindinfo')
       with:
@@ -53,7 +53,7 @@ jobs:
     - name: Run issues assignment to project SIG DDL Kanban
       uses: srggrs/[email protected]
       if: |
-        contains(github.event.issue.labels.*.name, 'component/DDL') ||
+        contains(github.event.issue.labels.*.name, 'sig/DDL') ||
         contains(github.event.issue.labels.*.name, 'component/binlog') ||
         contains(github.event.issue.labels.*.name, 'component/charset') ||
         contains(github.event.issue.labels.*.name, 'component/infoschema') ||