Added Bloomberg as a Platinum Sponsor, got rid of empty Sliver tier

Reviewed-by: Anton Arapov <anton@openssl.org>
Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Mark J. Cox <mark@awe.com>
(Merged from #472)

Author: sapkkaj

support/acks.md

@@ -33,20 +33,22 @@ note sponsors may choose to remain anonymous.
   }
 </style>
 
-### Gold:
+### Platinum:
 
 <div class="sponsorsection">
 
-[![Shiguredo Inc.](/img/shiguredo-logo-med.png){.sponsorlogo}](https://shiguredo.jp/)
-
-[![NetApp](/img/netapp-logo-med.jpg){.sponsorlogo}](https://www.netapp.com/)
+[![Bloomberg](/img/Bloomberg-LP-(Black).png){.sponsorlogo}](https://www.bloomberg.com/company/)
 
 </div>
 
-### Silver:
+### Gold:
 
 <div class="sponsorsection">
 
+[![Shiguredo Inc.](/img/shiguredo-logo-med.png){.sponsorlogo}](https://shiguredo.jp/)
+
+[![NetApp](/img/netapp-logo-med.jpg){.sponsorlogo}](https://www.netapp.com/)
+
 </div>
 
 ### Bronze: