fix: use copy of loop variable in parallel test (#23669)

This fixes an occurrence of a loop variable being captured in a
parallel test. With the previous code, only the last test case is
actually exercised. To work around this problem, we create a local
copy of the range variable before the parallel test, as suggested in
the Go documentation for the `testing` package:

https://pkg.go.dev/testing#hdr-Subtests_and_Sub_benchmarks

Issue was found automatically using the `loopvarcapture` linter.

sqlite/migrator_test.go

@@ -201,6 +201,7 @@ func TestScriptVersion(t *testing.T) {
 	}
 
 	for _, tt := range tests {
+		tt := tt // capture range variable
 		t.Run(tt.name, func(t *testing.T) {
 			t.Parallel()