burp: remove pre-activate block

Block added in a85edb8; can now be removed

sysutils/burp/Portfile

@@ -45,18 +45,6 @@ post-destroot {
 
 destroot.keepdirs ${destroot}${prefix}/etc/burp/CA-client
 
-pre-activate {
-    # Prevent activation failure for upgrades. This can be removed after January 2019.
-    # See https://trac.macports.org/ticket/55671
-    foreach filepath "${prefix}/etc/burp/CA-client/.turd_${subport}" {
-        if {[file exists ${filepath}] && [registry_file_registered ${filepath}] == "0"} {
-            if {[catch {delete ${filepath}}]} {
-                ui_warn "Cannot delete ${filepath}; please remove it manually"
-            }
-        }
-    }
-}
-
 livecheck.url ${homepage}/download.html
 livecheck.regex {<li>([0-9.]+): Stable$}