Update GHA runner image to latest Ubuntu (#5761)

`ubuntu-latest` means `ubuntu-20.04` at the time of the commit. It should always be a LTS version.

Author: kiview

.github/workflows/ci-docker-wormhole.yml

@@ -9,7 +9,7 @@ permissions:
 
 jobs:
   in-docker_test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
       - name: Build with Gradle

.github/workflows/ci-examples.yml

@@ -15,7 +15,7 @@ permissions:
 
 jobs:
   find_gradle_jobs:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
@@ -45,7 +45,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix: ${{ fromJson(needs.find_gradle_jobs.outputs.matrix) }}
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-java@v3

.github/workflows/ci-rootless.yml

@@ -9,7 +9,7 @@ permissions:
 
 jobs:
   test:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
       matrix:

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
       - id: thundra_test_initializer
         uses: thundra-io/thundra-test-init-action@v1
   find_gradle_jobs:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     outputs:
       matrix: ${{ steps.set-matrix.outputs.matrix }}
     steps:
@@ -51,7 +51,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix: ${{ fromJson(needs.find_gradle_jobs.outputs.matrix) }}
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-java@v3

.github/workflows/release.yml

@@ -13,7 +13,7 @@ permissions:
 
 jobs:
   release:
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-java@v3

.github/workflows/update-docs-version.yml

@@ -13,7 +13,7 @@ jobs:
       contents: write  # for peter-evans/create-pull-request to create branch
       pull-requests: write  # for peter-evans/create-pull-request to create a PR
     if: github.repository == 'testcontainers/testcontainers-java'
-    runs-on: ubuntu-18.04
+    runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
         with: