fix: remove username and change the subject in emails #1725

Job	Run time
Tests (ubuntu-20.04, 3.8, 16, django32-drflatest)	1m 17s
Tests (ubuntu-20.04, 3.8, 16, django40-drflatest)	1m 9s
Tests (ubuntu-20.04, 3.8, 16, django42-drflatest)	1m 21s
Tests (ubuntu-20.04, 3.8, 16, quality)	1m 26s
Tests (ubuntu-20.04, 3.8, 16, pii_check)	46s
Tests (ubuntu-20.04, 3.8, 16, version_check)	53s
Tests (ubuntu-20.04, 3.8, 16, js_tests)	1m 14s
Tests (ubuntu-20.04, 3.8, 16, js_lint)	57s
Tests (ubuntu-20.04, 3.8, 16, rst_validation)	38s
Tests (ubuntu-20.04, 3.8, 16, translations-django32)	1m 14s
Tests (ubuntu-20.04, 3.8, 16, translations-django42)	1m 0s
	11m 55s

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