bump: release v1.1.2 (#453)

## Release

This would mean tagging 595c710
`v1.1.2` to release.

## Vote

We need at least `4` approvals from `6` maintainers to release
`notation-go v1.1.2`.

- [x] Pritesh Bandi (@priteshbandi)
- [x] Junjie Gao (@JeyJeyGao)
- [ ] Rakesh Gariganti (@rgnote)
- [ ] Milind Gokarn (@gokarnm)
- [x] Shiwei Zhang (@shizhMSFT)
- [x] Patrick Zheng (@Two-Hearts)


## What's Changed
* fix&bump: maintenance update for branch `release-1.1` by @JeyJeyGao in
#448
* fix: dir no longer panics when HOME and XDG_CONFIG_HOME are not set
(#449) by @JeyJeyGao in
#450


**Full Changelog**:
v1.1.1...595c710

## Actions

Please review the PR and vote by approving.

Signed-off-by: Junjie Gao <[email protected]>

signer/signer.go

@@ -34,7 +34,7 @@ import (
 )
 
 // signingAgent is the unprotected header field used by signature.
-const signingAgent = "notation-go/1.1.2+unreleased"
+const signingAgent = "notation-go/1.1.2"
 
 // genericSigner implements notation.Signer and embeds signature.Signer
 type genericSigner struct {