upgrade to latest dependencies (#100)

bumping knative.dev/client 7e90dca...539a5a9:
  > 539a5a9 Add option to allow enviornment variables using file (# 1433)
  > 5d4b4f3 Fix windows e2e plugin tests (# 1457)
  > 09f14b1 Fix describe/list commands with json/yaml output format (# 1278)
  > 4760e52 Update changelog for 0.26 release (# 1456)
  > 99c70da upgrade to latest dependencies (# 1455)
  > d669111 upgrade to latest dependencies (# 1452)
  > e89bdc7 Update community files (# 1451)
  > ae5bce3 Update actions (# 1453)
  > 47558c1 Remove `DeprecatedImageDigest` field (# 1454)
  > 82a21a5 upgrade to latest dependencies (# 1448)
  > 94c8d33 Adding retry loop to update (# 1441)
  > dedcad7 upgrade to latest dependencies (# 1442)
  > 817068b Remove replace of go-openapi/spec from go.mod (# 1443)

Signed-off-by: Knative Automation <[email protected]>

Author: knative-automation

go.mod

@@ -5,7 +5,7 @@ go 1.15
 require (
 	github.com/spf13/cobra v1.2.1
 	gotest.tools/v3 v3.0.3
-	knative.dev/client v0.25.1-0.20210830145628-7e90dca8f3b4
+	knative.dev/client v0.25.1-0.20210921184138-539a5a97a692
 	knative.dev/hack v0.0.0-20210806075220-815cd312d65c
 
 )