Add note to README that Leap is no longer supported #6558

Job	Run time
Discover Versions	3s
Platform Cache / Discover Platforms	5s
Platform Cache / Build Platforms (none)	5s
Run Build Workflow / Build leap (reproducible)	8m 27s
Run Build Workflow / Build leap (asan)	11m 16s
Run Build Workflow / Build leap (ubuntu20)	7m 2s
Run Build Workflow / Build leap (ubsan)	9m 19s
Run Build Workflow / Build leap (ubuntu22)	7m 5s
Run Build Workflow / Build leap (asserton)	7m 50s
Build deb packages (ubuntu20)	12m 25s
Build deb packages (ubuntu22)	11m 53s
Tests (ubuntu20)	3m 32s
Build deb packages (reproducible)	14m 52s
Tests (ubuntu22)	3m 14s
LR Tests (ubuntu20)	23m 59s
NP Tests (ubuntu20)	6m 34s
LR Tests (ubuntu22)	24m 10s
Tests (asserton)	3m 15s
NP Tests (ubuntu22)	5m 5s
LR Tests (asserton)	23m 52s
Tests (ubsan)	4m 4s
NP Tests (asserton)	5m 10s
LR Tests (ubsan)	25m 25s
Tests (asan)	5m 51s
NP Tests (ubsan)	7m 53s
LR Tests (ubuntu20repro)	24m 16s
Tests (ubuntu20repro)	3m 29s
NP Tests (ubuntu20repro)	6m 12s
LR Tests (ubuntu22repro)	24m 9s
Tests (ubuntu22repro)	3m 14s
NP Tests (ubuntu22repro)	5m 7s
libtester tests (ubuntu22, build-tree)	9m 16s
libtester tests (ubuntu22, make-dev-install)	6m 13s
libtester tests (ubuntu22, deb-install)	1m 4s
All Required Tests Passed	1s
	5h 15m 27s

Provide feedback