Remove dependency on time crate

Version 0.1 of the `time` crate has a vulnerability. Apparently it does not affect the `chrono` crate, which is the crate that depends on `time`, but it's better to be safe. We don't actually need the default `chrono` feature of `fatfs`, so we can easily remove both `chrono` and `time` from our dependency tree by disabling that feature.

Author: phil-opp

Cargo.lock

@@ -23,7 +23,7 @@ members = [
     "tests/test_kernels/higher_half",
     "tests/test_kernels/pie",
     "tests/test_kernels/lto",
-    "tests/test_kernels/ramdisk"
+    "tests/test_kernels/ramdisk",
 ]
 exclude = ["examples/basic", "examples/test_framework"]
 
@@ -45,7 +45,10 @@ uefi = ["dep:gpt", "bootloader_test_runner/uefi"]
 
 [dependencies]
 anyhow = "1.0.32"
-fatfs = "0.3.4"
+fatfs = { version = "0.3.4", default-features = false, features = [
+    "std",
+    "alloc",
+] }
 tempfile = "3.3.0"
 mbrman = { version = "0.5.1", optional = true }
 gpt = { version = "3.0.0", optional = true }