[ci] Update to ubuntu-22.04 GitHub actions runner

Signed-off-by: Michael Brown <mcb30@ipxe.org>

.github/workflows/build.yml

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index f8ba4e1..b6e18e3 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -6,7 +6,7 @@
 
   x86:
     name: x86
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Check out code
         uses: actions/checkout@v3
@@ -32,7 +32,7 @@
 
   arm32:
     name: ARM32
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Check out code
         uses: actions/checkout@v3
@@ -52,7 +52,7 @@
 
   arm64:
     name: ARM64
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Check out code
         uses: actions/checkout@v3

.github/workflows/coverity.yml

diff --git a/.github/workflows/coverity.yml b/.github/workflows/coverity.yml
index d27eae1..ba86818 100644
--- a/.github/workflows/coverity.yml
+++ b/.github/workflows/coverity.yml
@@ -8,7 +8,7 @@
 jobs:
   submit:
     name: Submit
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Check out code
         uses: actions/checkout@v3