Added SK_PARAGRAPH_LIBTXT_SPACES_RESOLUTION to flutter_defines.gni

as a reminder that what we do here is not right and we only need it
temporary for Flutter.
Bug: skia:10715

Change-Id: I186edd3f761db72d2973c1128e0d95a78bd332f7
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/335220
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Julia Lavrova <jlavrova@google.com>

Author: Rusino

gn/flutter_defines.gni

@@ -11,6 +11,9 @@ flutter_defines = [
   # Remove software rasterizers to save some code size.
   "SK_DISABLE_AAA",
 
+  # Things we do for Flutter but don't want in general text layout
+  "SK_PARAGRAPH_LIBTXT_SPACES_RESOLUTION",
+
   # Staging
   "SK_SUPPORT_LEGACY_MATRIX_FACTORIES",