Fix capitalization of "GitHub". (#21257)

Author: waywardmonkeys

site/source/docs/api_reference/Filesystem-API.rst

@@ -31,7 +31,7 @@ The JavaScript-based file system was originally written before pthreads were sup
 
 `Design Doc Link <https://docs.google.com/document/d/1-ZxybGvz0nCqygUDuWxCcCBhCebev3EbUSYoSOlc49Q/edit?usp=sharing>`_
 
-`Github Tracking Issue <https://github.com/emscripten-core/emscripten/issues/15041>`_
+`GitHub Tracking Issue <https://github.com/emscripten-core/emscripten/issues/15041>`_
 
 Differences you may notice with the original JS filesystem include:
 

site/source/docs/porting/simd.rst

@@ -1152,7 +1152,7 @@ instructions which operate on 128-bit wide vectors are supported
 cleanly. This means that nearly any instruction which is not of a "q"
 variant (i.e. "vaddq" as opposed to "vadd") will be scalarized.
 
-These are pulled from `SIMDe repository on Github
+These are pulled from `SIMDe repository on GitHub
 <https://github.com/simd-everywhere/simde>`_. To update emscripten
 with the latest SIMDe version, run `tools/simde_update.py`.