timeutil: remove detritus windows Now() implementation

We carried a custom implementation of timeutil.Now() for Windows, to
overcome the low precision of Go's implementation [1]. Our
implementation was expensive, though. Having this custom implementation
also makes it tricky to use stdlib functions like Since(), which
internally use the stdlib Now().
The Golang issue has since been fixed, so our custom implementation can
go away.

[1] golang/go#8687

Release note: None

pkg/testutils/lint/lint_test.go

@@ -724,8 +724,6 @@ func TestLint(t *testing.T) {
 			"--",
 			"*.go",
 			":!**/embedded.go",
-			":!util/timeutil/now_unix.go",
-			":!util/timeutil/now_windows.go",
 			":!util/timeutil/time.go",
 			":!util/timeutil/zoneinfo.go",
 			":!util/tracing/span.go",

pkg/util/timeutil/BUILD.bazel

@@ -4,8 +4,6 @@ go_library(
     name = "timeutil",
     srcs = [
         "manual_time.go",
-        "now_unix.go",
-        "now_windows.go",
         "stopwatch.go",
         "time.go",
         "time_source.go",
@@ -20,12 +18,7 @@ go_library(
     deps = [
         "//pkg/util/syncutil",
         "@com_github_cockroachdb_errors//:errors",
-    ] + select({
-        "@io_bazel_rules_go//go/platform:windows": [
-            "@org_golang_x_sys//windows",
-        ],
-        "//conditions:default": [],
-    }),
+    ],
 )
 
 go_test(

pkg/util/timeutil/time.go

@@ -18,6 +18,11 @@ import (
 // LibPQTimePrefix is the prefix lib/pq prints time-type datatypes with.
 const LibPQTimePrefix = "0000-01-01"
 
+// Now returns the current UTC time.
+func Now() time.Time {
+	return time.Now().UTC()
+}
+
 // Since returns the time elapsed since t.
 // It is shorthand for Now().Sub(t).
 func Since(t time.Time) time.Duration {