Remove Alpine 3.15 - end of life (#1191)

Alpine 3.15 end of life was 1 Nov 2023

Author: MarkEWaite

.github/dependabot.yml

@@ -40,17 +40,6 @@ updates:
     schedule:
       interval: "weekly"
 
-  # Maintain dependencies for Alpine 3.15
-  - package-ecosystem: "docker"
-    directory: "src/test/resources/org/jvnet/hudson/plugins/platformlabeler/alpine/3.15.10"
-    ignore:
-    - dependency-name: "alpine"
-      update-types: ["version-update:semver-minor"]
-    labels:
-    - "skip-changelog"
-    schedule:
-      interval: "weekly"
-
   # Maintain dependencies for Alpine 3.16
   - package-ecosystem: "docker"
     directory: "src/test/resources/org/jvnet/hudson/plugins/platformlabeler/alpine/3.16.7"

README.md

@@ -13,7 +13,6 @@ Labels commonly include operating system name, version, architecture, and Window
 | Alibaba Linux 3            | `AlibabaCloud`     | `3`            | `amd64`      | // EOL: 30 Apr 2031
 | Alma Linux 8               | `AlmaLinux`        | `8.8`          | `amd64`      | // EOL: 31 Mar 2029
 | Alma Linux 9               | `AlmaLinux`        | `9.2`          | `amd64`      | // EOL: 31 May 2032
-| Alpine 3.15                | `Alpine`           | `3.15.9`       | `amd64`      | // EOL: 01 Nov 2023
 | Alpine 3.16                | `Alpine`           | `3.16.6`       | `amd64`      | // EOL: 01 May 2024
 | Alpine 3.17                | `Alpine`           | `3.17.4`       | `amd64`      | // EOL: 01 Nov 2024
 | Alpine 3.18                | `Alpine`           | `3.18.4`       | `amd64`      | // EOL: 01 May 2025

src/test/java/org/jvnet/hudson/plugins/platformlabeler/PlatformDetailsTest.java

@@ -130,7 +130,6 @@ void testDetailsWithoutFeatureUpdate() {
         "Windows 10", "alpine", "centos", "debian", "fedora", "freebsd", "macos", "raspbian", "ubuntu"
     };
     private final String[] versions = {
-        "3.15.7",
         "3.16.4",
         "3.17.2",
         "3.18.4",