Warning for the installation instruction on README (#12025)

* warning for the installation instruction on README

* Update README.md

Co-authored-by: Jake Lishman <[email protected]>

---------

Co-authored-by: Jake Lishman <[email protected]>

Author: 1ucian0

README.md

@@ -20,6 +20,9 @@ For more details on how to use Qiskit, refer to the documentation located here:
 
 ## Installation
 
+> [!WARNING]
+> Do not try to upgrade an existing Qiskit 0.* environment to Qiskit 1.0 in-place. [Read more](https://docs.quantum.ibm.com/api/migration-guides/qiskit-1.0-installation).
+
 We encourage installing Qiskit via ``pip``:
 
 ```bash