common: remove unused assert() headers.

Auditing for assert/abort in common/ code used by lightningd, this is all
that showed up.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

common/derive_basepoints.c

@@ -1,4 +1,3 @@
-#include <assert.h>
 #include <ccan/crypto/hkdf_sha256/hkdf_sha256.h>
 #include <ccan/crypto/sha256/sha256.h>
 #include <ccan/crypto/shachain/shachain.h>

common/funding_tx.c

@@ -1,5 +1,4 @@
 #include "funding_tx.h"
-#include <assert.h>
 #include <bitcoin/pubkey.h>
 #include <bitcoin/script.h>
 #include <bitcoin/tx.h>

lightningd/test/run-funding_tx.c

@@ -1,3 +1,4 @@
+#include <assert.h>
 #include <bitcoin/address.h>
 #include <bitcoin/base58.h>
 #include <bitcoin/privkey.h>