global: Drop useless casts to void *

src/lib-sieve/cmd-redirect.c

src/lib-sieve/cmp-i-octet.c

src/lib-sieve/ext-envelope.c

src/lib-sieve/ext-reject.c

src/lib-sieve/plugins/date/ext-date-common.c

src/lib-sieve/plugins/duplicate/ext-duplicate-common.c

src/lib-sieve/plugins/editheader/cmd-deleteheader.c

src/lib-sieve/plugins/editheader/ext-editheader-common.c

src/lib-sieve/plugins/enotify/cmd-notify.c

src/lib-sieve/plugins/enotify/ext-enotify-common.c

src/lib-sieve/plugins/enotify/ext-enotify.c

src/lib-sieve/plugins/enotify/mailto/ntfy-mailto.c

src/lib-sieve/plugins/environment/ext-environment-common.c

src/lib-sieve/plugins/ihave/ext-ihave-common.c

src/lib-sieve/plugins/imap4flags/tag-flags.c

src/lib-sieve/plugins/include/cmd-global.c

src/lib-sieve/plugins/include/ext-include-common.c

src/lib-sieve/plugins/include/ext-include-variables.c

src/lib-sieve/plugins/index/tag-index.c

src/lib-sieve/plugins/mailbox/tst-mailboxexists.c