Rename formats-util.h to format-util.h

We don't have plural in the name of any other -util files and this
inconsistency trips me up every time I try to type this file name
from memory. "formats-util" is even hard to pronounce.

src/machine/machine-dbus.c

@@ -37,7 +37,7 @@
 #include "env-util.h"
 #include "fd-util.h"
 #include "fileio.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "fs-util.h"
 #include "in-addr-util.h"
 #include "local-addresses.h"

src/machine/machine.c

@@ -30,7 +30,7 @@
 #include "extract-word.h"
 #include "fd-util.h"
 #include "fileio.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "hashmap.h"
 #include "machine-dbus.h"
 #include "machine.h"

src/machine/machined-dbus.c

@@ -30,7 +30,7 @@
 #include "cgroup-util.h"
 #include "fd-util.h"
 #include "fileio.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "hostname-util.h"
 #include "image-dbus.h"
 #include "io-util.h"

src/machine/machined.c

@@ -29,7 +29,7 @@
 #include "cgroup-util.h"
 #include "dirent-util.h"
 #include "fd-util.h"
-#include "formats-util.h"
+#include "format-util.h"
 #include "hostname-util.h"
 #include "label.h"
 #include "machine-image.h"