Update specs/fault-proof-vm.md

Co-authored-by: protolambda <proto@protolambda.com>

specs/fault-proof-vm.md

@@ -130,7 +130,7 @@ Consequently, the return value of read/write syscalls is at most 4, indicating t
 ### Standard Streams
 
 Writing to stderr/stdout standard stream always succeeds with the write count input returned, effectively continuing execution without writing work.
-Reading from stdin has no effect other than to return zero and errno set to 0.
+Reading from stdin has no effect other than to return zero and errno set to 0, signalling that there is no input.
 
 ### Hint Communication