Mark test snapshot files as linguist-generated (#5474)

Co-authored-by: Matt Rubens <[email protected]>

.gitattributes

@@ -1,3 +1,6 @@
 demo.gif filter=lfs diff=lfs merge=lfs -text
 assets/docs/demo.gif filter=lfs diff=lfs merge=lfs -text
 src/assets/docs/demo.gif filter=lfs diff=lfs merge=lfs -text
+
+# Test snapshot files - mark as linguist-generated to exclude from GitHub language statistics
+*.snap linguist-generated=true