fix dockerfile linter warning

Author: mattpolzin

.github/workflows/codecov.yml

@@ -5,7 +5,7 @@ on: [push]
 jobs:
   codecov:
     container: 
-      image: swift:5.10
+      image: swift:6.1
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3

.github/workflows/tests.yml

@@ -15,6 +15,8 @@ jobs:
         image:
           - swift:5.10-focal
           - swift:5.10-jammy
+          - swift:6.1-focal
+          - swift:6.1-jammy
     container: ${{ matrix.image }}
     steps:
     - name: Checkout code

Dockerfile

@@ -1,5 +1,5 @@
 
-FROM swift:5.10 as builder
+FROM swift:6.1 AS builder
 
 # Install OS updates and, if needed, sqlite3
 RUN export DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true \
@@ -52,7 +52,7 @@ RUN bin_path="$(swift build --package-path /build -c release --show-bin-path)" \
 ## Production image
 #
 
-FROM swift:5.10
+FROM swift:6.1
 
 # DEBIAN_FRONTEND=noninteractive for automatic UTC configuration in tzdata
 # Make sure all system packages are up to date.