Remove duplicated users from release announcement

Author: nicoddemus

doc/en/announce/release-6.0.0rc1.rst

@@ -19,7 +19,6 @@ Thanks to all who contributed to this release, among them:
 * Bruno Oliveira
 * Claire Cecil
 * Curt J. Sampson
-* Daniel
 * Daniel Hahler
 * Danny Sepler
 * David Diaz Barquero
@@ -30,7 +29,6 @@ Thanks to all who contributed to this release, among them:
 * Gleb Nikonorov
 * Hugo van Kemenade
 * Hunter Richards
-* Katarzyna
 * Katarzyna Król
 * Katrin Leinweber
 * Keri Volans
@@ -52,7 +50,6 @@ Thanks to all who contributed to this release, among them:
 * Tor Colvin
 * Xinbin Huang
 * Zac Hatfield-Dodds
-* Zac-HD
 * earonesty
 * gaurav dhameeja
 * gdhameeja