Without further information, the encircled links indicate channel bonding/trunking. Bonded channels (or LAG trunks, Etherchannel) are regarded as a single, logical link. STP doesn't block any of the physical links.
Even if the physical links to a server are not bonded, there's only half a bridge loop: the switch forwards frames solely based on the destination MAC address and which port this MAC is - currently - located on from the switch's perspective. The server is not likely to speak STP, so no ports are blocked.
When the ports are bonded on the server side, the switch may see the MACs flapping back and forth. Due to the nature of broadcasts, the server will also receive its own broadcasts back on the other port.
Only static trunks can be active on one side without the other. LACP protocol trunks always come up on both sides or not at all (STP will block the spare links between switches) - they should be preferred.
However, if there's some kind of switching software active on the server it behaves like a switch. With neither bonding nor STP active on the dual link you might have a bridge loop, depending on the nature of the switch software. For instance, an ESXi vSwitch never forwards from one physical link to another physical link, so it'll never cause a bridge loop.
An alternative way to use multiple links between a server and a switch is to use them as separate links. This may accomplish better load balancing but doesn't provide full redundancy without further measures.