update version to v1.7.5

[thinkerou]

as title

[codecov]

Codecov Report

Merging #2943 (a1767e3) into master (6aee456) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2943   +/-   ##
=======================================
  Coverage   98.73%   98.73%           
=======================================
  Files          41       41           
  Lines        3080     3080           
=======================================
  Hits         3041     3041           
  Misses         27       27           
  Partials       12       12           

Flag	Coverage Δ
go-1.13	98.73% <ø> (ø)
go-1.14	98.57% <ø> (ø)
go-1.15	98.57% <ø> (ø)
go-1.16	98.57% <ø> (ø)
go-1.17	98.47% <ø> (ø)
macos-latest	98.73% <ø> (ø)
nomsgpack	98.71% <ø> (ø)
ubuntu-latest	98.73% <ø> (ø)

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[thinkerou]

@appleboy please review, thanks!

[Bisstocuz]

Maybe should change CHANGELOG.md, too.
Provided a template below for saving your time.

---

Gin v1.7.5

DOCS

• NoMethod: added usage annotation (#2832).

BUGFIXES

• Fixed X-Forwarded-For unsafe handling of CVE-2020-28483 #2844, closed issue #2862.
• Tree: updated the code logic for latestNode #2897, closed issue #2894 #2878.
• Tree: fixed the misplacement of adding slashes #2847, closed issue #2843.
• Tree: fixed tsr with mixed static and wildcard paths #2924, closed issue #2918.

ENHANCEMENTS

• TrustedProxies: make it backward-compatible #2887, closed issue #2819.
• TrustedPlatform: provide custom options for another CDN services #2906.

---

You can change the logs as your wish:

## Gin v1.7.5
### DOCS

* NoMethod: added usage annotation ([#2832](https://github.com/gin-gonic/gin/pull/2832#issuecomment-929954463)).

### BUGFIXES

* Fixed X-Forwarded-For unsafe handling of CVE-2020-28483 [#2844](https://github.com/gin-gonic/gin/pull/2844), closed issue [#2862](https://github.com/gin-gonic/gin/issues/2862).
* Tree: updated the code logic for `latestNode` [#2897](https://github.com/gin-gonic/gin/pull/2897), closed issue [#2894](https://github.com/gin-gonic/gin/issues/2894) [#2878](https://github.com/gin-gonic/gin/issues/2878).
* Tree: fixed the misplacement of adding slashes [#2847](https://github.com/gin-gonic/gin/pull/2847), closed issue [#2843](https://github.com/gin-gonic/gin/issues/2843).
* Tree: fixed tsr with mixed static and wildcard paths [#2924](https://github.com/gin-gonic/gin/pull/2924), closed issue [#2918](https://github.com/gin-gonic/gin/issues/2918).

### ENHANCEMENTS

* TrustedProxies: make it backward-compatible [#2887](https://github.com/gin-gonic/gin/pull/2887), closed issue [#2819](https://github.com/gin-gonic/gin/issues/2819).
* TrustedPlatform: provide custom options for another CDN services [#2906](https://github.com/gin-gonic/gin/pull/2906).

[thinkerou]

@Bisstocuz thanks, updated!

[thinkerou]

@appleboy maybe we should release v1.8.0, and v1.8 list: https://github.com/gin-gonic/gin/milestone/16.
when we release v1.7.5, update go.mod firstly #2951

[thinkerou]

v1.7.7 have released, thanks! https://github.com/gin-gonic/gin/releases