upgrades postcss to address https://www.npmjs.com/advisories/1094239

[enekofb]

What changed?
upgrade postcss to fix found vulnerability

Why was this change made?

➜  weave-gitops git:(main) make ui-audit                                                                                                                                                                                                                                                                                
yarn audit --production
yarn audit v1.22.19
warning ../../../../package.json: No license field
┌───────────────┬──────────────────────────────────────────────────────────────┐
│ moderate      │ PostCSS line return parsing error                            │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Package       │ postcss                                                      │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Patched in    │ >=8.4.31                                                     │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Dependency of │ postcss                                                      │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Path          │ postcss                                                      │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ More info     │ https://www.npmjs.com/advisories/1094239                     │
└───────────────┴──────────────────────────────────────────────────────────────┘
1 vulnerabilities found - Packages audited: 975
Severity: 1 Moderate

How was this change implemented?

How did you validate the change?

Run it locally and UI looks functional

Release notes

Documentation Changes