Bump Security String to 2021-04-05

Implemented:
============
CVE:            References:     Type:   Severity:       Updated AOSP versions:
CVE-2021-0400   A-177561690     EoP     High            9, 10, 11
CVE-2021-0431   A-174149901     ID      High            8.1, 9, 10, 11
CVE-2021-0435   A-174150451     ID      High            8.1, 9, 10, 11
CVE-2021-0438   A-152064592     EoP     High            8.1, 9, 10
CVE-2021-0443   A-170474245     ID      High            8.1, 9, 10, 11

Previously Implemented:
============
CVE:            References:     Type:   Severity:       Updated AOSP versions:
None

Not Implemented:
================
CVE:            References:     Type:   Severity:       Updated AOSP versions:
None

Not Applicable (platform source):
=================================
CVE:            References:     Type:   Severity:       Updated AOSP versions:
CVE-2021-0426   A-174485572     EoP     High            11
CVE-2021-0427   A-174488848     EoP     High            11
CVE-2021-0428   A-173421434     ID      High            10
CVE-2021-0429   A-175074139     EoP     High            8.1, 9, 10, 11
CVE-2021-0430   A-178725766     RCE     Critical        10, 11
CVE-2021-0432   A-173552790     EoP     High            11
CVE-2021-0433   A-171221090     EoP     High            8.1, 9, 10, 11
CVE-2021-0436   A-176496160     ID      High            8.1, 9, 10, 11
CVE-2021-0437   A-176168330     EoP     High            8.1, 9, 10, 11
CVE-2021-0439   A-174243830     EoP     High            11
CVE-2021-0442   A-174768985     EoP     High            11
CVE-2021-0444   A-178825358     ID      High            8.1, 9, 10, 11
CVE-2021-0445   A-172322502     EoP     High            9, 11
CVE-2021-0446   A-172252122     EoP     High            11
CVE-2021-0471   A-176444786     ID      High            8.1, 9, 10, 11

Signed-off-by: Vasyl Gello <vasek.gello@gmail.com>
Change-Id: I7f62a816b61345ebb394ab98dc8ff7679f6bef13