Hi Phillip;
In your case being ESXi 5.5 and Build ID: 7618464, this update removed both the microcode updates and the framework to allow guest OSes to utilize the new speculative-execution control mechanisms. When the first microcode updates were released, ESXi 5.5 had 1 patch (framework and microcode), and ESXi 6.0 and 6.5 it was 2. VMware Knowledge Base
go ahead and update your 5.5 today. note that in this release the control mechanism is a separate patch not like the first release that was pulled.
Edgar