[ci skip] changelog header correction for 0.3.21
[ci skip] changelog header correction for 0.3.21

gliderlabs/herokuish,gliderlabs/herokuish,expa/herokuish,gliderlabs/herokuish,expa/herokuish,expa/herokuish,gliderlabs/herokuish,gliderlabs/herokuish,expa/herokuish,gliderlabs/herokuish,expa/herokuish,gliderlabs/herokuish,expa/herokuish,expa/herokuish,expa/herokuish,gliderlabs/herokuish