fix broken prev normalization #59

Job	Run time
Lint	2m 31s
Create VSIX	3m 17s
Check Python types	1m 45s
Coverage (ubuntu-latest)	4m 19s
Tests (ubuntu-latest, 3.x, ts-unit)	3m 0s
Tests (ubuntu-latest, 3.x, python-unit)	2m 51s
Tests (ubuntu-latest, 3.x, venv)	3m 41s
Tests (ubuntu-latest, 3.x, single-workspace)	4m 13s
Tests (ubuntu-latest, 3.x, debugger)	2m 20s
Tests (ubuntu-latest, 3.x, functional)	2m 11s
Tests (windows-latest, 3.x, ts-unit)	4m 19s
Tests (windows-latest, 3.x, python-unit)	3m 58s
Tests (windows-latest, 3.x, venv)	6m 9s
Tests (windows-latest, 3.x, single-workspace)	5m 20s
Tests (windows-latest, 3.x, debugger)	5m 22s
Tests (windows-latest, 3.x, functional)	3m 43s
Smoke tests (ubuntu-latest)	4m 14s
Smoke tests (windows-latest)	7m 2s
	1h 10m 15s

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