Add changelog for 3.7.4-RC3

Author: WojciechMazur

changelogs/3.7.4-RC3.md

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+# Backported chnages
+
+- Lint avoids revisiting Inlined.call [#24277](https://github.com/scala/scala3/pull/24277)
+- Register no elements for lint after inlining [#24279](https://github.com/scala/scala3/pull/24279)
+- Use enclosing enclosingInlineds for empty call [#24281](https://github.com/scala/scala3/pull/24281)
+- Exclude synthetic opaque proxy from lint [#24264](https://github.com/scala/scala3/pull/24264)
+- Deprecate `scala_legacy`/`MainGenericRunner`/`scalac -run`/`scalac -repl` for removal [#24267](https://github.com/scala/scala3/pull/24267)
+
+# Contributors
+
+Thank you to all the contributors who made this release possible 🎉
+
+According to `git shortlog -sn --no-merges 3.7.4-RC2..3.7.4-RC4` these are:
+
+```
+  4  Wojciech Mazur
+  2  Piotr Chabelski
+  2  Som Snytt
+```