build(github): fixing build runner to ubuntu 20.04

Trying to get plugin to work with redis 6.2.4 docker image.

Author: markmcdowell

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ concurrency:
   cancel-in-progress: true
 jobs:
   ci:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@v4

.github/workflows/release.yml

@@ -6,7 +6,7 @@ on:
       - v*
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v4
       - uses: actions-rs/cargo@v1.0.3