[#1474] Stop using obsolete .github directory

This commit is a part of multi-repo cleanup effort:
TrueCloudLab/frostfs-infra#136

Signed-off-by: Vitaliy Potyarkin <v.potyarkin@yadro.com>

README.md

@@ -1,5 +1,5 @@
 <p align="center">
-  <img src="./.github/logo.svg" width="500px" alt="FrostFS">
+  <img src="./.forgejo/logo.svg" width="500px" alt="FrostFS">
 </p>
 
 <p align="center">

docs/release-instruction.md

@@ -55,7 +55,7 @@ Add an entry to the `CHANGELOG.md` following the style established there.
 * update `Unreleased...new` and `new...old` diff-links at the bottom of the file
 * add optional codename and release date in the heading
 * remove all empty sections such as `Added`, `Removed`, etc.
-* make sure all changes have references to GitHub issues in `#123` format (if possible)
+* make sure all changes have references to relevant issues in `#123` format (if possible)
 * clean up all `Unreleased` sections and leave them empty
 
 ### Make release commit
@@ -110,9 +110,9 @@ $ docker push truecloudlab/frostfs-cli:${FROSTFS_REVISION}
 $ docker push truecloudlab/frostfs-adm:${FROSTFS_REVISION}
 ```
 
-### Make a proper GitHub release (if not automated)
+### Make a proper release (if not automated)
 
-Edit an automatically-created release on GitHub, copy things from `CHANGELOG.md`.
+Edit an automatically-created release on git.frostfs.info, copy things from `CHANGELOG.md`.
 Build and tar release binaries with `make prepare-release`, attach them to
 the release. Publish the release.
 
@@ -121,7 +121,7 @@ the release. Publish the release.
 Prepare pull-request in [frostfs-devenv](https://git.frostfs.info/TrueCloudLab/frostfs-dev-env)
 with new versions.
 
-### Close GitHub milestone
+### Close milestone
 
 Look up [milestones](https://git.frostfs.info/TrueCloudLab/frostfs-node/milestones) and close the release one if exists.
 

docs/update-go-instruction.md

@@ -7,7 +7,7 @@
 ## Update CI
 
 Change Golang versions for unit test in CI.
-There is `go` section in `.github/workflows/go.yaml` file:
+There is `go` section in `.forgejo/workflows/*.yml` files:
 ```yaml
 jobs:
   test: