[Release Notes Appender] Add PR #7754: index-shipper: add support for multiple stores (#10306)

Add PR #7754 to release notes for next release

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Co-authored-by: Ashwanth Goli <iamashwanth@gmail.com>

docs/sources/release-notes/next.md

@@ -13,3 +13,6 @@ Grafana Labs is excited to announce the release of Loki ?.?. Here's a summary of
 ## Features and enhancements
 
 -  **Query Language Improvements**: Several improvements to the query language that speed up line parsing and regex matching. [PR #8646](https://github.com/grafana/loki/pull/8646), [PR #8659](https://github.com/grafana/loki/pull/8659), [PR #8724](https://github.com/grafana/loki/pull/8724), [PR #8734](https://github.com/grafana/loki/pull/8734), [PR #8739](https://github.com/grafana/loki/pull/8739), [PR #8763](https://github.com/grafana/loki/pull/8763), [PR #8890](https://github.com/grafana/loki/pull/8890),[PR #8914](https://github.com/grafana/loki/pull/8914)
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+-  **Multi-store Index support**: Loki now supports reading/writing indexes to multiple object stores which enables the use of different storage buckets across periods for storing index. [PR #7754](https://github.com/grafana/loki/pull/7754)], [PR #7447](https://github.com/grafana/loki/pull/7447)
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