Remove excessive newlines in 'README.md' files

Author: regexident

stun/CHANGELOG.md

@@ -6,7 +6,6 @@
 
 * Increased minimum support rust version to `1.60.0`.
 * Increased required `webrtc-util` version to `0.7.0`.
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 ## v0.4.3
 
@@ -16,4 +15,3 @@
 ## Prior to 0.4.3
 
 Before 0.4.3 there was no changelog, previous changes are sometimes, but not always, available in the [GitHub Releases](https://github.com/webrtc-rs/stun/releases).
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