chore: fix formatting

Author: gnidan

packages/web/spec/program/context/function/invoke.mdx

@@ -21,7 +21,7 @@ contexts to reconstruct call stacks.
 
 ## Pointer evaluation and instruction placement
 
-An instruction's context describes what is known *following*
+An instruction's context describes what is known _following_
 that instruction's execution: the fact that a function was
 invoked holds from that point forward. Pointers within the
 context reference the machine state at the instruction's trace