[infra] Update to newer rpmalloc library.

Upstream rpmalloc fixed its bug that prevented compilation with
recent Clang toolchain releases, so drop the custom patching of
its `build/ninja/clang.py` file.

This CL also adjusts the way the rpmalloc sources are obtained,
by taking them from the `upstream/develop` branch of the Fuchsia
provided git mirror, which tracks the Github upstream closely,
as opposed with the `develop` branch on the same repository that
is seriously dated now.

Bug: None
Change-Id: I90eeddafa0cbd3acf815d8c00300ce04fb4199cf
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/13520
Reviewed-by: Petr Hosek <phosek@google.com>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: David Turner <digit@google.com>
diff --git a/infra/README.recipes.md b/infra/README.recipes.md
index 5a6ea74..731d098 100644
--- a/infra/README.recipes.md
+++ b/infra/README.recipes.md
@@ -101,7 +101,7 @@
 
 Recipe for building GN.
 
-&mdash; **def [RunSteps](/infra/recipes/gn.py#105)(api, repository):**
+&mdash; **def [RunSteps](/infra/recipes/gn.py#106)(api, repository):**
 ### *recipes* / [macos\_sdk:examples/full](/infra/recipe_modules/macos_sdk/examples/full.py)
 
 [DEPS](/infra/recipe_modules/macos_sdk/examples/full.py#7): [macos\_sdk](#recipe_modules-macos_sdk), [recipe\_engine/platform][recipe_engine/recipe_modules/platform], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/step][recipe_engine/recipe_modules/step]