fix(@schematics/angular): use bracket notation for `process.env['pm_i… #2050

Job	Run time
build	24s
build-e2e-windows	35s
lint	2m 16s
Browser Compatibility Tests	0s
publish-snapshots	0s
test	0s
e2e	0s
e2e-package-managers	0s
e2e-snapshots	0s
e2e-windows	-1s
	3m 14s

Provide feedback