build: remove faketime unsetting and comments from configure.ac

configure.ac

@@ -42,14 +42,9 @@ AH_TOP([#ifndef BITCOIN_CONFIG_H])
 AH_TOP([#define BITCOIN_CONFIG_H])
 AH_BOTTOM([#endif //BITCOIN_CONFIG_H])
 
-dnl faketime breaks configure and is only needed for make. Disable it here.
-unset FAKETIME
-
 dnl Automake init set-up and checks
 AM_INIT_AUTOMAKE([1.13 no-define subdir-objects foreign])
 
-dnl faketime messes with timestamps and causes configure to be re-run.
-dnl --disable-maintainer-mode can be used to bypass this.
 AM_MAINTAINER_MODE([enable])
 
 dnl make the compilation flags quiet unless V=1 is used