Testing: Remove sd.Valid()

[jannotti]

Summary

It was not used anywhere. Presumably, it was written thinking that a StateDelta would be check after making it. But instead, each step of creating the StateDelta is checked.

Test Plan

I guess if it compiles, I was right!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 51.85%. Comparing base (8118cfe) to head (abaf278).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6323      +/-   ##
==========================================
- Coverage   51.86%   51.85%   -0.02%     
==========================================
  Files         652      652              
  Lines       87442    87425      -17     
==========================================
- Hits        45353    45335      -18     
+ Misses      39227    39226       -1     
- Partials     2862     2864       +2     

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[cce]

Non-test references removed in #1765
found this using git bisect with:

#!/usr/bin/env bash
set -euo pipefail
sym_line="$(gopls symbols "data/basics/teal.go" 2>/dev/null | grep -m1 'StateDelta).Valid Method' || true)"
if [[ -z "$sym_line" ]]; then
  exit 1
fi
pos_range="${sym_line##* }"
start_pos="${pos_range%%-*}"
line_no="${start_pos%%:*}"
col_no="${start_pos##*:}"
ref_total="$(gopls references "data/basics/teal.go:${line_no}:${col_no}" 2>/dev/null || true)"
non_test_count="$(printf '%s\n' "$ref_total" | grep -v '_test\.go:' | grep -c .)"
if (( non_test_count > 0 )); then
  exit 0
else
  exit 1 
fi