GHA/curl-for-win: disable `DOCKER_CONTENT_TRUST`

As a workaround for the latest Debian image missing the necessary keys:
```
No signatures for debian:testing-20240926-slim

Administrative keys for debian:testing-20240926-slim

  Repository Key:       5717dcd81d9fb5b73aa15f2d887a6a0de543829ab9b2d411acce9219c2f8ba3a
  Root Key:     575d013f89e3cbbb19e0fb06aa33566c22718318e0c9ffb1ab5cc4291e07bf84
No valid trust data for testing-20240926-slim
```
https://github.com/curl/curl/actions/runs/11067644862/job/30752034560?pr=15065

Ref: https://github.com/curl/curl-for-win/commit/0ad1ad511bcbfbad8935685f7c130b281e66f7f4

diff --git a/.github/workflows/curl-for-win.yml b/.github/workflows/curl-for-win.yml
index 134749bd2c6292533aacdbcc64cb9c3853074375..923924ca4f9404414a093c1c97e32278bf39f7c9 100644 (file)
--- a/.github/workflows/curl-for-win.yml
+++ b/.github/workflows/curl-for-win.yml
@@ -40,7 +40,7 @@ env:
   CW_MAP: '0'
   CW_JOBS: '5'
   CW_NOPKG: '1'
-  DOCKER_CONTENT_TRUST: '1'
+  DOCKER_CONTENT_TRUST: ''
 
 jobs:
   linux-glibc-llvm: