doc/go1.18: add a release note for 'go mod tidy' checksum changes
doc/go1.18: add a release note for 'go mod tidy' checksum changes

Updates #47738
Fixes #49598

Change-Id: I708dcb880a701699116227a9eaca994cf460fef9
Reviewed-on: https://go-review.googlesource.com/c/go/+/378577
Trust: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Run-TryBot: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Trust: Daniel Martí <29bf28b42a938ace12a5819da4ed4ba03d82f315@mvdan.cc>
Reviewed-by: Daniel Martí <29bf28b42a938ace12a5819da4ed4ba03d82f315@mvdan.cc>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/go,nawawi/go,golang/go,cloudflare/go,cloudflare/go,CAFxX/go,golang/go,cloudflare/go,nawawi/go,CAFxX/go,nawawi/go,golang/go,golang/go,nawawi/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,CAFxX/go,nawawi/go,CAFxX/go,CAFxX/go,cloudflare/go,golang/go,golang/go,cloudflare/go,nawawi/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,cloudflare/go