GN: Fix some typos in the documentation.

tools/gn/variables.cc

Index: tools/gn/variables.cc
diff --git a/tools/gn/variables.cc b/tools/gn/variables.cc
index d387baeb726244d6756044c1d87fef57762b6767..3b60c903557eb603c1f035f63c0d34ce87f28e66 100644
--- a/tools/gn/variables.cc
+++ b/tools/gn/variables.cc
@@ -416,7 +416,7 @@ const char kAllDependentConfigs_Help[] =
   This addition happens in a second phase once a target and all of its
   dependencies have been resolved. Therefore, a target will not see these
   force-added configs in their "configs" variable while the script is running,
-  and then can not be removed. As a result, this capability should generally
+  and they can not be removed. As a result, this capability should generally
   only be used to add defines and include directories necessary to compile a
   target's headers.
 
@@ -1575,7 +1575,7 @@ const char kPublicConfigs_Help[] =
   This addition happens in a second phase once a target and all of its
   dependencies have been resolved. Therefore, a target will not see these
   force-added configs in their "configs" variable while the script is running,
-  and then can not be removed. As a result, this capability should generally
+  and they can not be removed. As a result, this capability should generally
   only be used to add defines and include directories necessary to compile a
   target's headers.