fix readme about kotlinc_opts and javac_opts

[asinbow]

As the title.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[asinbow]

According to

rules_kotlin/kotlin/internal/jvm/jvm.bzl

Lines 217 to 230 in ebef8c5

	"kotlinc_opts": attr.label(
	doc = """Kotlinc options to be used when compiling this target. These opts if provided
	will be used instead of the ones provided to the toolchain.""",
	default = None,
	providers = [_KotlincOptions],
	mandatory = False,
	),
	"javac_opts": attr.label(
	doc = """Javac options to be used when compiling this target. These opts if provided will
	be used instead of the ones provided to the toolchain.""",
	default = None,
	providers = [_JavacOptions],
	mandatory = False,
	),

.