build: fix macos builds by working around travis osx flaw (#30479)

This should fix https://github.com/ethereum/go-ethereum/issues/30471.
See investigation in https://github.com/ethereum/go-ethereum/pull/30478
for more background.

.travis.yml

@@ -85,7 +85,7 @@ jobs:
       if: type = push
       os: osx
       osx_image: xcode14.2
-      go: 1.23.x
+      go: 1.23.1 # See https://github.com/ethereum/go-ethereum/pull/30478
       env:
         - azure-osx
       git: