build(deps): bump alpine from 3.18.2 to 3.18.3 in /frps

Bumps alpine from 3.18.2 to 3.18.3.

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

frps/Dockerfile

@@ -4,7 +4,7 @@
 # https://github.com/fatedier/frp
 
 # Build environment
-FROM alpine:3.18.2 AS build 
+FROM alpine:3.18.3 AS build 
 ARG TARGETOS
 ARG TARGETARCH
 ARG FRP_VERSION