Use a longer pack key

There should be no difference if we use 32 random bytes or more, since
GPG's longest symmetric key is 32 bytes, but to just remove any doubt we
use a longer random passphrase.

git-remote-gcrypt

@@ -17,7 +17,7 @@ Localdir="${GIT_DIR:=.git}/remote-gcrypt"
 export GITCEPTION="${GITCEPTION:-}+" # Reuse $Gref except when stacked
 Gref="refs/gcrypt/gitception$GITCEPTION"
 Gref_rbranch="refs/heads/master"
-Packkey_bytes=33  # 33 random bytes for passphrase, still compatible if changed
+Packkey_bytes=63  # nbr random bytes for packfile keys, any >= 256 bit is ok
 Hashtype=SHA256   # SHA512 SHA384 SHA256 SHA224 supported.
 Manifestfile=91bd0c092128cf2e60e1a608c31e92caf1f9c1595f83f2890ef17c0e4881aa0a
 Hex40="[a-f0-9]"