gitiles seems to mangle the links when viewed from
https://boringssl.googlesource.com/boringssl/+/master/README.md, but not
https://boringssl.googlesource.com/boringssl/.

This document suggests that it handles absolute and relative links to files
specially. I guess it didn't interpret 'README.md' as either and failed to adjust
it accordingly. Let's see if this works instead.

https://gerrit.googlesource.com/gitiles/+/master/Documentation/markdown.md#Links

Change-Id: Ic181919140f968c88c69ea8f3c21c70f63e4b467
Reviewed-on: https://boringssl-review.googlesource.com/6230
Reviewed-by: Adam Langley <agl@google.com>

Change-Id: I77b1d0efa6cddfcb162be693d53276822780540f
Reviewed-on: https://boringssl-review.googlesource.com/5790
Reviewed-by: Adam Langley <agl@google.com>