Python: version updated to 1.28.0 (#11504)

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Updated the version of the package to 1.28

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- [x] The code builds clean without any errors or warnings
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Author: eavanvalkenburg

python/semantic_kernel/__init__.py

@@ -2,7 +2,7 @@
 
 from semantic_kernel.kernel import Kernel
 
-__version__ = "1.27.2"
+__version__ = "1.28.0"
 
 DEFAULT_RC_VERSION = f"{__version__}-rc6"