build: Increase Go version to 1.20.7

.github/workflows/build-syncthing.yaml

@@ -11,7 +11,7 @@ env:
   # The go version to use for builds. We set check-latest to true when
   # installing, so we get the latest patch version that matches the
   # expression.
-  GO_VERSION: "^1.20.3"
+  GO_VERSION: "^1.20.7"
 
   # Optimize compatibility on the slow archictures.
   GO386: softfloat