DM/PDF: stop adding unused rasterizer keywords

We can always add it back if we need it in the future.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1852713002

Review URL: https://codereview.chromium.org/1852713002
diff --git a/tools/flags/SkCommonFlagsConfig.cpp b/tools/flags/SkCommonFlagsConfig.cpp
index 1ee3130..7d43207 100644
--- a/tools/flags/SkCommonFlagsConfig.cpp
+++ b/tools/flags/SkCommonFlagsConfig.cpp
@@ -28,7 +28,7 @@
 static const char configHelp[] =
     "Options: 565 8888 debug gpu gpudebug gpudft gpunull "
     "msaa16 msaa4 gpuf16 gpusrgb nonrendering null nullgpu "
-    "nvpr16 nvpr4 nvprdit16 nvprdit4 pdf pdf_poppler skp svg xps"
+    "nvpr16 nvpr4 nvprdit16 nvprdit4 pdf skp svg xps"
 #if SK_ANGLE
 #ifdef SK_BUILD_FOR_WIN
     " angle"