Bump Security String to 2021-03-05

Implemented:
============
CVE:            References:     Type:   Severity:       Updated AOSP versions:
CVE-2017-14491  A-158221622     RCE     High            8.1, 9, 10, 11
CVE-2021-0391   A-172841550     EoP     High            8.1, 9, 10, 11
CVE-2021-0393   A-168041375     RCE     High            8.1, 9, 10, 11
CVE-2021-0394   A-172655291     ID      High            8.1, 9, 10, 11
CVE-2021-0396   A-160610106     RCE     High            8.1, 9, 10, 11
CVE-2021-0397   A-174052148     RCE     Critical        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-2021-0390   A-174749461     EoP     High            8.1, 9, 10, 11
CVE-2021-0392   A-175124730     EoP     High            9, 10, 11
CVE-2021-0395   A-170315126     EoP     High            11
CVE-2021-0398   A-173516292     EoP     High            11

Signed-off-by: Vasyl Gello <vasek.gello@gmail.com>
Change-Id: I93197be1cac9ecca75407ea758e3e71979ccda20