Avoid unnecessary `RST_STREAM` frames in HTTP/2 implementation

[v0idpwn]

When a stream is locally closed and a EndStream flag is received, Mint is sending RST_STREAM with NO_ERROR.
This is unnecessary as a stream can be deemed closed by both sides at this point, and this frame is just ignored.

[whatyouhide]

Good catch @v0idpwn. Wanna make a PR to fix this? 🙃

[v0idpwn]

Yeah, will try to send one soon!