doc: Remove "temporary file" notice from 0.17.0 release notes

not that temporary anymore

Tree-SHA512: c44bfca71573b3d70001d339138715fc6fbceae2e370f2e1e8ba5bdfdb19e8ec4b0a59d45ff8565e0f784d4659f51e8089a6d892a73362b428d8a98097fc8532

doc/release-notes/release-notes-0.17.0.md

@@ -1,6 +1,3 @@
-(note: this is a temporary file, to be added-to by anybody, and moved to
-release-notes at release time)
-
 Bitcoin Core version 0.17.0 is now available from:
 
   <https://bitcoincore.org/bin/bitcoin-core-0.17.0/>
@@ -1105,4 +1102,4 @@ And to those that reported security issues:
 
 - awemany (for CVE-2018-17144, previously credited as "anonymous reporter")
 
-As well as everyone that helped translating on [Transifex](https://www.transifex.com/projects/p/bitcoin/).
+As well as everyone that helped translating on [Transifex](https://www.transifex.com/projects/p/bitcoin/).