Prepare release 4.8.0

Bump version.props from 4.7.0 to 4.8.0.

Changes in 4.8.0 (from RELEASE_NOTES.md):
- Added AsyncSeq.mapFoldAsync
- Added AsyncSeq.mapFold
- Added AsyncSeq.allPairs
- Added AsyncSeq.rev

Co-authored-by: Copilot <[email protected]>

Author: github-actions[bot]

version.props

@@ -1,5 +1,5 @@
 <Project>
   <PropertyGroup>
-    <Version>4.7.0</Version>
+    <Version>4.8.0</Version>
   </PropertyGroup>
 </Project>