Fix minor GYP error in webrtc/tools/internal_tools.gyp

It seems 'deps' is similar to 'dependencies' for the ninja and make
generators in GYP, but some generators does not support it.
Better use the correct key.
This was introduced in https://codereview.webrtc.org/1387243002/

TBR=phoglund@webrtc.org

Review URL: https://codereview.webrtc.org/1386353003 .

Cr-Commit-Position: refs/heads/master@{#10200}
diff --git a/webrtc/tools/internal_tools.gyp b/webrtc/tools/internal_tools.gyp
index 40dc371..61000d1 100644
--- a/webrtc/tools/internal_tools.gyp
+++ b/webrtc/tools/internal_tools.gyp
@@ -20,7 +20,7 @@
         'simple_command_line_parser.h',
         'simple_command_line_parser.cc',
       ],
-      'deps': [
+      'dependencies': [
         '<(webrtc_root)/common.gyp:gtest_prod',
       ],
     }, # command_line_parser