replace 'Which' with 'which'

Change-Id: I8462f8762fed97c0acaea893bfb332c7eba6e6a5
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/15300
Reviewed-by: David Turner <digit@google.com>
Commit-Queue: Takuto Ikuta <tikuta@google.com>

docs/reference.md

diff --git a/docs/reference.md b/docs/reference.md
index 093c711..eca3032 100644
--- a/docs/reference.md
+++ b/docs/reference.md
@@ -2462,7 +2462,7 @@
 
   You can also check a named scope using a subscript string expression:
     defined(foo[bar + "_name"])
-  Which will return true or false depending on whether the subscript
+  which will return true or false depending on whether the subscript
   expression expands to the name of a member of the scope foo. It will
   throw an error if foo is not defined or is not a scope, or if the
   expression does not expand to a string, or if it is an empty string.

src/gn/functions.cc

diff --git a/src/gn/functions.cc b/src/gn/functions.cc
index e41d688..3ca1588 100644
--- a/src/gn/functions.cc
+++ b/src/gn/functions.cc
@@ -516,7 +516,7 @@
 
   You can also check a named scope using a subscript string expression:
     defined(foo[bar + "_name"])
-  Which will return true or false depending on whether the subscript
+  which will return true or false depending on whether the subscript
   expression expands to the name of a member of the scope foo. It will
   throw an error if foo is not defined or is not a scope, or if the
   expression does not expand to a string, or if it is an empty string.