collector/diskstats: Don't use functions from Go 1.18

Since we need to support Go 1.17, don't use `strings.Cut()` which was
introduced in Go 1.18.

Signed-off-by: Benoît Knecht <bknecht@protonmail.ch>

collector/diskstats_linux.go

@@ -361,9 +361,15 @@ func udevDeviceInformation(major, minor uint32) (udevInfo, error) {
 
 	scanner := bufio.NewScanner(data)
 	for scanner.Scan() {
+		/* TODO: After we drop support for Go 1.17, the condition below can be simplified to:
+
 		if name, value, found := strings.Cut(scanner.Text(), "="); found {
 			info[name] = value
 		}
+		*/
+		if fields := strings.SplitN(scanner.Text(), "=", 2); len(fields) == 2 {
+			info[fields[0]] = fields[1]
+		}
 	}
 
 	return info, nil