doc: dovecot.conf is 644 file permission, not 755

Use INSTALL_DATA instead of INSTALL in doc/Makefile.am to install
dovecot.conf with 644 instead of 755 file permission. After the patch,
after `./autogen.sh; ./configure`, doc/Makefile shows dovecot.conf is
correctly installed with INSTALL_DATA which is `/usr/bin/install -c -m
644` instead of INSTALL which is `/usr/bin/install -c`. More info about
INSTALL_DATA see `info make`.

Signed-off-by: Xiao Pan <[email protected]>

Author: flyxyz123

doc/Makefile.am

@@ -26,7 +26,7 @@ all-local: stamp-man
 install-data-hook:
 	$(INSTALL) -d $(DESTDIR)$(sysconfdir)/dovecot
 	test -e $(DESTDIR)$(sysconfdir)/dovecot/dovecot.conf || \
-	$(INSTALL) dovecot.conf $(DESTDIR)$(sysconfdir)/dovecot/dovecot.conf
+	$(INSTALL_DATA) dovecot.conf $(DESTDIR)$(sysconfdir)/dovecot/dovecot.conf
 
 install-data-local:
 	$(MKDIR_P) $(DESTDIR)$(docdir); \