Remove exists example for now

README.md

@@ -20,14 +20,6 @@ Proof.
   iPureIntro.
   exact (Himpl HP2).
 Qed.
-
-Lemma exists_demo P1 (P2: nat -> PROP) :
-  P1 ∗ (∃ x, P2 x) -∗ ∃ x, P1 ∗ P2 x.
-Proof.
-  iIntros "[? [%x HP2]]".
-  iFrame.
-  iExists x; iExact "HP2".
-Qed.
 ```
 
 ## Acknowledgements