btrfs-progs: ci: move Leap image to 15.6

The support of Leap 15.4 has ended, not much point to test build there
so move it to 15.6 (upper bound). The lower bound is still 15.3 to catch
potential backward compatibility problems.

The hub image exists (https://hub.docker.com/r/kdave/ci-opensuse-leap-15.6-x86_64).

Signed-off-by: David Sterba <dsterba@suse.com>

.github/workflows/ci-build-test-fast.yml

@@ -30,12 +30,12 @@ jobs:
     steps:
       - name: CI Leap 15.3
         run: sudo docker run kdave/ci-opensuse-leap-15.3-x86_64 ./test-build $GITHUB_REF_NAME --disable-documentation --disable-zoned
-  check-leap154:
-    name: CI Leap 15.4
+  check-leap156:
+    name: CI Leap 15.6
     runs-on: ubuntu-24.04
     steps:
-      - name: CI Leap 15.4
-        run: sudo docker run kdave/ci-opensuse-leap-15.4-x86_64 ./test-build $GITHUB_REF_NAME --disable-documentation --disable-zoned
+      - name: CI Leap 15.6
+        run: sudo docker run kdave/ci-opensuse-leap-15.6-x86_64 ./test-build $GITHUB_REF_NAME --disable-documentation --disable-zoned
   check-musl:
     name: CI Musl
     runs-on: ubuntu-24.04

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

@@ -31,13 +31,13 @@ jobs:
       - uses: actions/checkout@v4
       - name: CI Leap 15.3
         run: ci/ci-build-leap153
-  check-leap154:
-    name: CI Leap 15.4
+  check-leap156:
+    name: CI Leap 15.6
     runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
-      - name: CI Leap 15.4
-        run: ci/ci-build-leap154
+      - name: CI Leap 15.6
+        run: ci/ci-build-leap156
   check-musl:
     name: CI Musl
     runs-on: ubuntu-24.04

ci/ci-build-leap156

@@ -1,6 +1,6 @@
 #!/bin/sh
 # Usage: $0 [branch] [configure options]
-# Create source tarball from HEAD or given branch and build it in openSUSE Leap 15.4 CI
+# Create source tarball from HEAD or given branch and build it in openSUSE Leap 15.6 CI
 # environment. Configure options follow branch name that can be empty.
 
 HERE=`pwd`
@@ -14,7 +14,7 @@ else
 	exit 1
 fi
 
-CIIMAGEDIR=ci/images/ci-openSUSE-Leap-15.4-x86_64
+CIIMAGEDIR=ci/images/ci-openSUSE-Leap-15.6-x86_64
 BRANCH=${1:-HEAD}
 if [ "$#" -ge 1 ]; then
 	shift

ci/images/ci-openSUSE-Leap-15.6-x86_64/Dockerfile

@@ -1,4 +1,4 @@
-FROM opensuse/leap:15.4
+FROM opensuse/leap:15.6
 
 WORKDIR /tmp