Drop github workflows with python 3.8

.github/workflows/phonopy-pytest-conda-openmp.yml

@@ -18,7 +18,7 @@ jobs:
         shell: bash -l {0}
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
 
     steps:
     - uses: actions/checkout@v4

.github/workflows/phonopy-pytest-conda.yml

@@ -18,7 +18,7 @@ jobs:
         shell: bash -l {0}
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11", "3.12"]
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
 
     steps:
     - uses: actions/checkout@v4

.github/workflows/publish-gh-pages.yml

@@ -12,11 +12,11 @@ jobs:
         shell: bash -l {0}
     strategy:
       matrix:
-        python-version: ["3.11"]
+        python-version: ["3.12"]
 
     steps:
-    - uses: actions/checkout@v2
-    - uses: conda-incubator/setup-miniconda@v2
+    - uses: actions/checkout@v4
+    - uses: conda-incubator/setup-miniconda@v3
       with:
         auto-update-conda: true
         channels: conda-forge

.github/workflows/publish-to-test-pypi.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.12, ]
+        python-version: ["3.12"]
 
     steps:
     - uses: actions/checkout@v4