Fix issue where spacers with more than 500 height were being resized automatically to 500 when opening settings

GB PR: WordPress/gutenberg#20984

To test:

• Open the demo app
• Add a spacer block
• Switch to HTML mode
• Change the height of the spacer to something larger than 500
• Switch to visual mode
• Open the setting of the block
• Check that you can see the larger value and edit the value.

PR submission checklist:

• I have considered adding unit tests where possible.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.