Avoid the use of ` in log messages and comments

src/lib-managesieve/managesieve-url.c

src/lib-sieve/cmd-redirect.c

src/lib-sieve/ext-envelope.c

src/lib-sieve/ext-fileinto.c

src/lib-sieve/ext-reject.c

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

src/lib-sieve/plugins/date/tst-date.c

src/lib-sieve/plugins/duplicate/tst-duplicate.c

src/lib-sieve/plugins/editheader/cmd-addheader.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/mailto/ntfy-mailto.c

src/lib-sieve/plugins/environment/tst-environment.c

src/lib-sieve/plugins/ihave/tst-ihave.c

src/lib-sieve/plugins/imap4flags/ext-imap4flags-common.c

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

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

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

src/lib-sieve/plugins/metadata/tst-metadata.c