Strip xml strings for ttx tables

[rsheeter]

python resources/scripts/ttx_diff.py 'https://github.com/docrepair-fonts/lugrasimo-fonts#sources/Lugrasimo-Regular.designspace' --compare gftools --config ~/.fontc_crater_cache/docrepair-fonts/lugrasimo-fonts/sources/config.yaml reports gasp 88.9%. If we diff the table ttx it seems to differ only in trailing newline:

# These tables look the same ... but ttx_diff reports them different
$ diff -u build/gftools/fontc.gasp.ttx build/gftools/fontmake.gasp.ttx
--- build/gftools/fontc.gasp.ttx	2025-01-22 22:54:39
+++ build/gftools/fontmake.gasp.ttx	2025-01-22 22:54:39
@@ -2,4 +2,3 @@
     <gaspRange rangeMaxPPEM="65535" rangeGaspBehavior="15"/>
   </gasp>
 
-  
\ No newline at end of file

# ttx reports the same length and checksum for the gasp produced by both compilers.

Strip the table xml to avoid such issues. The ttx_diff cmd above now reports gasp identical.