[SYCL][DOC] Close the ABI breaking changes window (#10561)

Next one is expected to be around same time frame, Apr-July 2024

Author: stdale-intel

sycl/doc/developer/ABIPolicyGuide.md

@@ -103,20 +103,5 @@ owners for help.
 **Note**: Features clearly marked as experimental are considered as an exception
 to this guideline.
 
-### ABI breaking changes window April 18 - July 11 2023
-
-During this period of time ABI breaking changes will be accepted. All breaking 
-changes will still require a good justification.
-
-Whenever you need to change the existing ABI, please, follow these steps:
-
-1. Add [ABI-break] tag to your PR title.
-2. Update your PR description with rationale why breaking ABI is necessary.
-3. Fix failing ABI tests in your Pull Request. Use aforementioned techniques to
-   update test files.
-4. Increment library engineering version together with the change ("-V" postfix
-   part of version, as described above)
-
-At the end of this window we will increment major version of the DPC++ library
-
-Next ABI breaking changes window is April 2024.
+### ABI breaking changes window April 18 - July 11 2023 [CLOSED]
+Next ABI breaking changes window is tenatively April 2024.