fix(tests): unskip dolt_clean zero-argument tests

Issue #1361 reported that SELECT DOLT_CLEAN() with no arguments failed
with "function dolt_clean() does not exist". This was fixed in PR #1763
which added Function0 registration for all Dolt procedures, but the
corresponding tests in dolt_functions_test.go remained skipped.

Note: PR #1373 (referenced by issue #1361) also added skipped tests in
prepared_statement_test.go, but those were already unskipped in commit
62569c7 ("finished removing custom expr type").

List of changes below:
- Remove Skip: true from zero-argument DOLT_CLEAN() tests
- Reorder test assertions so DOLT_CLEAN('t1') runs before DOLT_CLEAN()
- Add table recreation step between test cases to verify both work

Refs: #1361

Author: codeaucafe

testing/go/dolt_functions_test.go

@@ -2746,12 +2746,19 @@ func TestDoltFunctionSmokeTests(t *testing.T) {
 					},
 				},
 				{
-					Skip:     true, // TODO: function dolt_clean() does not exist
-					Query:    "SELECT DOLT_CLEAN();",
+					Query:    "SELECT DOLT_CLEAN('t1');",
 					Expected: []sql.Row{{"{0}"}},
 				},
 				{
-					Query:    "SELECT DOLT_CLEAN('t1');",
+					Query:    "SELECT * FROM dolt.status;",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "CREATE TABLE t1 (pk int primary key);",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "SELECT DOLT_CLEAN();",
 					Expected: []sql.Row{{"{0}"}},
 				},
 				{
@@ -2769,12 +2776,10 @@ func TestDoltFunctionSmokeTests(t *testing.T) {
 					},
 				},
 				{
-					Skip:     true, // TODO: function dolt_clean() does not exist
 					Query:    "SELECT DOLT_CLEAN();",
 					Expected: []sql.Row{{"{0}"}},
 				},
 				{
-					Skip:     true,
 					Query:    "SELECT * FROM dolt.status;",
 					Expected: []sql.Row{},
 				},