Improve case clarify for syntax templates

src/dynamic-import/empty-args-early-error.case

src/dynamic-import/empty-str-arg.case

...yntax/invalid/nested-arrow-assignment-expression.template

src/dynamic-import/syntax/invalid/nested-arrow.template

...mport/syntax/invalid/nested-async-function-await.template

...yntax/invalid/nested-async-function-return-await.template

...amic-import/syntax/invalid/nested-async-function.template

...namic-import/syntax/invalid/nested-block-labeled.template

src/dynamic-import/syntax/invalid/nested-block.template

src/dynamic-import/syntax/invalid/nested-do-while.template

src/dynamic-import/syntax/invalid/nested-do.template

...amic-import/syntax/invalid/nested-else-braceless.template

src/dynamic-import/syntax/invalid/nested-else.template

...mic-import/syntax/invalid/nested-function-return.template

src/dynamic-import/syntax/invalid/nested-function.template

...ynamic-import/syntax/invalid/nested-if-braceless.template

src/dynamic-import/syntax/invalid/nested-if.template

src/dynamic-import/syntax/invalid/nested-labeled.template

src/dynamic-import/syntax/invalid/nested-while.template

src/dynamic-import/syntax/invalid/top-level.template