style(functions): remove blank line in sponge_filter_secrets.fish header

The man-page comment header was separated from the function line by a
blank line -- the only file in functions/ with that gap. Cosmetic, no
runtime effect (manualtools and the help-flag renderer both tolerate
it by walking past a blank separator). See JOB-BRIEF-FINDINGS.md §2;
the renderer's tolerance for this case is left in place deliberately,
it is not dead code.

functions/sponge_filter_secrets.fish

@@ -31,7 +31,6 @@
 # EXAMPLE
 #   # Register with sponge (done automatically by conf.d/sponge_privacy.fish):
 #   set -U -a sponge_filters sponge_filter_secrets
-
 function sponge_filter_secrets --argument-names command
     # Find all exported variables with security-sensitive names
     set -l sensitive_vars (set --names --export | string match --regex -- \