Fix duplicate aesthetics warning in ggsurv() for upcoming ggplot2

[Copilot]

ggplot2's upcoming release warns when aesthetics are specified both in aes() and as fixed parameters. ggsurv() specified lty in both locations for confidence interval bounds, triggering warnings that fail the expect_silent() test.

Changes

• R/ggsurv.R: Removed lty = .data$group from aes() in confidence interval geom_step() calls (lines 335, 340). The fixed lty = stepLty parameter remains and provides the intended behavior.
• NEWS.md: Added entry documenting the fix

Before/After

# Before - duplicate lty specification
geom_step(
  aes(y = .data$up, lty = .data$group, col = .data$group),  # lty here
  lty = stepLty,                                             # and here
  linewidth = size.ci
)

# After - single lty specification
geom_step(
  aes(y = .data$up, col = .data$group),
  lty = stepLty,
  linewidth = size.ci
)

Verified that removing the aesthetic mapping does not change plot output, as noted by @schloerke.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Heads up: duplicate aesthetics will get warning</issue_title>
<issue_description>Hi Barett and other maintainers,

We recently did a revdepcheck in ggplot2 and found that a new check we introduced got triggered by GGally. In particular we now throw a warning which violates this test:

ggally/tests/testthat/test-ggsurv.R

Lines 72 to 74 in d21c6d6

	expect_silent(
	ggsurv(sf.kid, CI = TRUE, surv.col = c("black", "red", "blue", "green"))
	)

I believe the warning is thrown because lty is used twice in these layer definitions, once in aes() and once as a fixed parameter:

ggally/R/ggsurv.R

Lines 333 to 343 in d21c6d6

	pl <- pl +
	geom_step(
	aes(y = .data$up, lty = .data$group, col = .data$group),
	lty = stepLty,
	linewidth = size.ci
	) +
	geom_step(
	aes(y = .data$low, lty = .data$group, col = .data$group),
	lty = stepLty,
	linewidth = size.ci
	)

We've no immediate plans to release a ggplot2 that includes the check, but just wanted to simply flag this for the future.

Cheers!</issue_description>

<agent_instructions>Please add a NEWS.md entry</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@schloerke Thank you!

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Local testing shows that if we remove aes(lty= .data$group), the plots are the same. We should keep the geom_step arg.

Before making any changes, we should verify that an error is thrown in the test when using the dev version of ggplot2

• Fixes Heads up: duplicate aesthetics will get warning #571

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