Remove placeholder code

actions/ql/src/Placeholder.ql

@@ -1,16 +0,0 @@
-/**
- * @name Placeholder Query
- * @description Placeholder
- * @kind problem
- * @problem.severity warning
- * @security-severity 9.3
- * @precision high
- * @id actions/placeholder
- * @tags actions security
- */
-
-import actions
-import javascript
-
-from File f
-select f, "Analyzed a file."

actions/ql/test/library-tests/Placeholder.expected

@@ -1 +0,0 @@
-| 1 |

actions/ql/test/library-tests/Placeholder.ql

@@ -1 +0,0 @@
-select 1

actions/ql/test/query-tests/Placeholder/.github/workflows/shell.yml

@@ -1,23 +0,0 @@
-on: push
-
-jobs:
-  job1:
-    runs-on: ubuntu-latest
-    steps:
-      - shell: pwsh
-        run: Write-Output "foo"
-  job2:
-    runs-on: ubuntu-latest
-    steps:
-      - run: echo "foo"
-
-  job3:
-    runs-on: windows-latest
-    steps:
-      - shell: bash
-        run: echo "foo"
-  job4:
-    runs-on: windows-latest
-    steps:
-      - run: Write-Output "foo"
-

actions/ql/test/query-tests/Placeholder/Placeholder.expected

@@ -1 +0,0 @@
-| .github/workflows/shell.yml:0:0:0:0 | .github/workflows/shell.yml | Analyzed a file. |

actions/ql/test/query-tests/Placeholder/Placeholder.qlref

@@ -1 +0,0 @@
-Placeholder.ql