internal/dl: update minimum Linux kernel to 2.6.32

All supported Go versions, that is Go 1.18 and newer, now share a
common Linux kernel version requirement adopted in proposal 45964.

For golang/go#45964.

Change-Id: Iec386b75f71ebf192883e4aac9bb3634bffdfe35
Reviewed-on: https://go-review.googlesource.com/c/website/+/424574
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Run-TryBot: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>

internal/dl/dl.go

@@ -175,7 +175,7 @@ var featuredFiles = []Feature{
 	},
 	{
 		Platform:     "Linux",
-		Requirements: "Linux 2.6.23 or later, Intel 64-bit processor",
+		Requirements: "Linux 2.6.32 or later, Intel 64-bit processor",
 		fileRE:       regexp.MustCompile(`\.linux-amd64\.tar\.gz$`),
 	},
 	{