EOL changes to alpine(3.18)

Author: sireeshajonnalagadda

src/base-alpine/README.md

@@ -9,7 +9,7 @@
 | *Categories* | Core, Other |
 | *Image type* | Dockerfile |
 | *Published images* | mcr.microsoft.com/devcontainers/base:alpine |
-| *Available image variants* | alpine-3.21, alpine-3.20, alpine-3.19, alpine-3.18 ([full list](https://mcr.microsoft.com/v2/devcontainers/base/tags/list)) |
+| *Available image variants* | alpine-3.21, alpine-3.20, alpine-3.19 ([full list](https://mcr.microsoft.com/v2/devcontainers/base/tags/list)) |
 | *Published image architecture(s)* | x86-64, aarch64/arm64 |
 | *Container host OS support* | Linux, macOS, Windows |
 | *Container OS* | Alpine Linux |
@@ -25,7 +25,6 @@ You can also directly reference pre-built versions of `.devcontainer/Dockerfile`
 - `mcr.microsoft.com/devcontainers/base:alpine-3.21`
 - `mcr.microsoft.com/devcontainers/base:alpine-3.20`
 - `mcr.microsoft.com/devcontainers/base:alpine-3.19`
-- `mcr.microsoft.com/devcontainers/base:alpine-3.18`
 
 Refer to [this guide](https://containers.dev/guide/dockerfile) for more details.
 

src/base-alpine/manifest.json

@@ -3,8 +3,7 @@
 	"variants": [
 		"3.21",		
 		"3.20",
-		"3.19",
-		"3.18"
+		"3.19"
 	],
 	"build": {
 		"latest": false,