footnote fixup

Author: tholok97

docs/sonar-3d/sonar-3d-15-api.md

@@ -25,11 +25,9 @@ This is the structure of a RIP2 packet:
 |-|-|
 |4|0x82 0x73 0x80 0x50, Identifier which reads “RIP2” in ASCII|
 |4|Packet length (including identifier, packet length, payload and checksum)|
-|payload length [^1]|Encoded protobuf message, compressed with [Snappy](https://en.wikipedia.org/wiki/Snappy_(compression))|
+|payload length (packet length - 12)|Encoded protobuf message, compressed with [Snappy](https://en.wikipedia.org/wiki/Snappy_(compression))|
 |4|IEEE 802.3 CRC-32 of the preceding bytes in the packet|
 
-[^1]: payload length is packet length - 12.
-
 **Decoding Steps**:
 
 1. Verify the `RIP2` ID.