Remove python 3.8 (#471)

Remove 3.8 for all workflows and matrices

Also use Ubuntu-22 for coverage task to avoid some as yet undiagnosed
issue with `lcov` on `ubuntu-latest` which is now `ubuntu-24`

.github/workflows/build-test-cplusplus.yml

@@ -16,7 +16,7 @@ concurrency:
 
 jobs:
   coverage:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout code
         uses: actions/checkout@v4

.github/workflows/build-test-riscv64.yml

@@ -24,8 +24,6 @@ jobs:
       matrix:
         os: [ubuntu-latest]
         python:
-          - major-dot-minor: "3.8"
-            matrix: "3.8"
           - major-dot-minor: "3.9"
             matrix: "3.9"
           - major-dot-minor: "3.10"

.github/workflows/doc-html-pdf.yml

@@ -22,7 +22,7 @@ jobs:
     - uses: actions/setup-python@v5
       name: Install Python
       with:
-        python-version: '3.8'
+        python-version: '3.10'
 
     - name: Install python markdown
       shell: bash

.github/workflows/plot-k27-no-bitfield.yaml

@@ -30,7 +30,7 @@ jobs:
     - uses: actions/setup-python@v5
       name: Install Python
       with:
-        python-version: '3.8'
+        python-version: '3.10'
 
     - name: cmake, Plot k=27
       run: |

.github/workflows/plot-k27.yaml

@@ -30,7 +30,7 @@ jobs:
     - uses: actions/setup-python@v5
       name: Install Python
       with:
-        python-version: '3.8'
+        python-version: '3.10'
 
     - name: cmake, Plot k=27
       run: |