style: freeze the resolved-tables carrier

Same reasoning as PhysicalOptimizerRules gaining frozen on the base
branch: nothing mutates it between resolve and commit, so there is no
reason to pay for the runtime borrow flag a mutable pyclass carries.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: timsaucer

crates/core/src/context.rs

@@ -1894,7 +1894,8 @@ impl PySessionContext {
 /// [`PyPhysicalOptimizerRules`]. Each entry is a provider that has already been
 /// imported and a schema that has already been looked up, so committing is an
 /// insert into a resolved destination rather than a fresh name resolution.
-#[pyclass(name = "ResolvedTables", module = "datafusion._internal")]
+/// `frozen` for the same reason as its sibling: the commit only reads.
+#[pyclass(frozen, name = "ResolvedTables", module = "datafusion._internal")]
 pub struct PyResolvedTables {
     tables: Vec<ResolvedTable>,
 }