Update Dockerfile and README to use ccarpinteri's pia-wg-config v1.4.0 for improved PIA WireGuard region selection

Dockers/gluetun-pia-wireguard-rotator/Dockerfile

@@ -1,7 +1,9 @@
-FROM golang:1.23-alpine AS builder
+FROM golang:1.25-alpine AS builder
 
+# ccarpinteri fork: uses PIA's central token API instead of regional
+# /authv3/generateToken (CN-only certs fail on modern Go / new Server-* hosts).
 RUN apk add --no-cache git ca-certificates \
-    && go install github.com/kylegrantlucas/pia-wg-config@v1.1.1
+    && go install github.com/ccarpinteri/pia-wg-config@v1.4.0
 
 FROM docker:cli