[cleanup] Remove stale documentation from get_target_outputs.

The if statement starting at line 122 in the left-side diff rejects binary targets.
This CL simply updates the documentation to reflect that current reality.

Change-Id: I745c4c8f894c8c6c7d2d85e57b981ff0d598777b
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/5960
Reviewed-by: Brett Wilson <brettw@chromium.org>
Commit-Queue: Brett Wilson <brettw@chromium.org>

tools/gn/function_get_target_outputs.cc

diff --git a/tools/gn/function_get_target_outputs.cc b/tools/gn/function_get_target_outputs.cc
index 711536d..83e7356 100644
--- a/tools/gn/function_get_target_outputs.cc
+++ b/tools/gn/function_get_target_outputs.cc
@@ -45,12 +45,6 @@
   process_file_template will return for those inputs (see "gn help
   process_file_template").
 
-  binary targets (executables, libraries): this will return a list of the
-  resulting binary file(s). The "main output" (the actual binary or library)
-  will always be the 0th element in the result. Depending on the platform and
-  output type, there may be other output files as well (like import libraries)
-  which will follow.
-
   source sets and groups: this will return a list containing the path of the
   "stamp" file that Ninja will produce once all outputs are generated. This
   probably isn't very useful.