Update golang.org/x/text to 0.3.3+ CVE-2020-14040 in SGW 2.8.x

SyncGateway 2.8.x has a High Severity vulnerability in the golang.org/x/text library.

HIGH:https://nvd.nist.gov/vuln/detail/CVE-2020-14040

The x/text package before 0.3.3 for Go has a vulnerability in encoding/unicode that could lead to the UTF-16 decoder entering an infinite loop, causing the program to crash or run out of memory. An attacker could provide a single byte to a UTF16 decoder instantiated with UseBOM or ExpectBOM to trigger an infinite loop if the String function on the Decoder is called, or the Decoder is passed to golang.org/x/text/transform.String.

Ben Brooks - confirmed via slack that SGW 2.8.3 is using a version that's between v0.3.0 and v0.3.1 (which will be affected by the CVE)
https://github.com/couchbase/sync_gateway/blob/40f04c91d21a4d82db4927b6fc18bacd0862c0b9/manifest/2.8.xml#L78