Remove azure-mgmt-trustedsigning source from main (#47348)

Package has been deprecated and released as 1.0.1. Remove source from main per the deprecation process; source remains available under the azure-mgmt-trustedsigning_1.0.1 release tag. Only the package README.md is kept.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: msyyc

sdk/trustedsigning/azure-mgmt-trustedsigning/CHANGELOG.md

@@ -1,3 +1,7 @@
 # Microsoft Azure SDK for Python
 
 This package has been deprecated and will no longer be maintained after 06-04-2026. This package will only receive security fixes until 06-04-2026. To receive updates on new features and non-security bug fixes, upgrade to the replacement package, [azure-mgmt-artifactsigning](https://pypi.org/project/azure-mgmt-artifactsigning/).
+
+Package source code and samples have been removed from the `main` branch and can be found under the release tag for the latest version. See [azure-mgmt-trustedsigning_1.0.1](https://github.com/Azure/azure-sdk-for-python/tree/azure-mgmt-trustedsigning_1.0.1/sdk/trustedsigning/azure-mgmt-trustedsigning). The latest release can be found on [PyPI](https://pypi.org/project/azure-mgmt-trustedsigning/).
+
+If you have any questions, please open a [GitHub Issue](https://github.com/Azure/azure-sdk-for-python/issues) or email `azpysdkhelp@microsoft.com`.