Updating FP16's README.chromium to include Revision

Revision is already provided in Version field. No version tags were found to be associated with this revision, so leaving Version as is.

R=nigi@chromium.org, npm@chromium.org

Bug: 350851535
Change-Id: I8ac466af8aa802bba13242b7e0057400735b5452
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/121573
Auto-Submit: Jordan Brown <rop@google.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/third_party/fp16/README.pdfium b/third_party/fp16/README.pdfium
index 1015e01..2fd397a 100644
--- a/third_party/fp16/README.pdfium
+++ b/third_party/fp16/README.pdfium
@@ -2,6 +2,7 @@
 Short Name: fp16
 URL: https://github.com/Maratyszcza/FP16
 Version: 0a92994d729ff76a58f692d3028ca1b64b145d91
+Revision: 0a92994d729ff76a58f692d3028ca1b64b145d91
 Date: 2022/10/24
 License: MIT
 License File: LICENSE