chore(deps): add syrupy>=5.1.0 for docs widget snapshot tests

syrupy provides the ``snapshot`` assertion fixture used by the
forthcoming widget highlight-parity tests to record byte-level HTML
for regression catch. Chosen to match gp-sphinx's own docs tests
(which use the same version) so the snapshot-fixture pattern ports
over verbatim.

Author: tony

pyproject.toml

@@ -69,6 +69,7 @@ dev = [
   "pytest-mock",
   "pytest-watcher",
   "pytest-xdist",
+  "syrupy>=5.1.0",
   # Coverage
   "codecov",
   "coverage",