fix: stop 'experimentalScopedSlotChanges' warning msg on startup

[johnjenkins]

What is the current behavior?

Given stencil.config options

extras: {
    experimentalSlotFixes: true,
  },

a warning shows:

If the 'experimentalSlotFixes' flag is enabled it will override any slot fix flags which are disabled. In
particular, the following currently-disabled flags will be ignored: experimentalScopedSlotChanges. Please
update your Stencil config accordingly.

This was introduced in #6055 due to experimentalScopedSlotChanges not being explicitly set (and defaulting to false) when experimentalSlotFixes is set.

GitHub Issue Number: N/A

What is the new behavior?

No warnings

Documentation

Does this introduce a breaking change?

• Yes
• No

Testing

Other information

[christian-bromann]

LGTM 👍