Remove clang_use_chrome_plugins=false from README

This no longer seems necessary, and clang_use_chrome_plugins=true is the
default where supported.

Change-Id: I88eca88c6e7dfb0b9cb54fc336acb3951baa212d
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/79130
Auto-Submit: K. Moon <kmoon@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
diff --git a/README.md b/README.md
index cf603a5..e8b1437 100644
--- a/README.md
+++ b/README.md
@@ -103,8 +103,6 @@
 pdf_enable_v8 = true  # Set false to remove Javascript support.
 pdf_is_standalone = true  # Set for a non-embedded build.
 is_component_build = false # Disable component build (Though it should work)
-
-clang_use_chrome_plugins = false  # Currently must be false.
 ```
 
 For sample applications like `pdfium_test` to build, one must set