Update relative links to Linux docs

This is a followup to [1].

[1] https://chromium-review.googlesource.com/c/chromium/src/+/1974901

TBR=sky

Change-Id: I442ffe121378607bdc5e1b16c081b8d66b138955
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1980900
Reviewed-by: Thomas Anderson <[email protected]>
Commit-Queue: Thomas Anderson <[email protected]>
Cr-Commit-Position: refs/heads/master@{#727226}
diff --git a/docs/linux/pid_namespace_support.md b/docs/linux/pid_namespace_support.md
index 81ce80f..0b282c84 100644
--- a/docs/linux/pid_namespace_support.md
+++ b/docs/linux/pid_namespace_support.md
@@ -1,6 +1,6 @@
 # Linux PID Namespace Support
 
-The [LinuxSUIDSandbox](linux_suid_sandbox.md) currently relies on support for
+The [LinuxSUIDSandbox](suid_sandbox.md) currently relies on support for
 the `CLONE_NEWPID` flag in Linux's
 [clone() system call](http://www.kernel.org/doc/man-pages/online/pages/man2/clone.2.html).
 You can check whether your system supports PID namespaces with the code below,