Bump up the minimum required MySQL version (#25465)

MySQL 5.7 is at end of life.

https://mattermost.atlassian.net/browse/MM-55589

```release-note
We bump up minimum MySQL version to be 8.0.0
```


Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: Ibrahim Serdar Acikgoz <serdaracikgoz86@gmail.com>

server/channels/store/sqlstore/store.go

@@ -52,8 +52,7 @@ const (
 	// 9.6.3 would be 90603.
 	minimumRequiredPostgresVersion = 110000
 	// major*1000 + minor*100 + patch
-	minimumRequiredMySQLVersion    = 5712
-	minimumRecommendedMySQLVersion = 8000
+	minimumRequiredMySQLVersion = 8000
 
 	migrationsDirectionUp   migrationDirection = "up"
 	migrationsDirectionDown migrationDirection = "down"
@@ -1232,9 +1231,6 @@ func (ss *SqlStore) ensureMinimumDBVersion(ver string) (bool, error) {
 			return false, fmt.Errorf("cannot parse MySQL DB version: %w", err2)
 		}
 		intVer := majorVer*1000 + minorVer*100 + patchVer
-		if intVer < minimumRecommendedMySQLVersion {
-			mlog.Warn("The MySQL version being used is EOL. Please upgrade to a later version.", mlog.Int("current_version", intVer), mlog.Int("minimum_recommended_version", minimumRecommendedMySQLVersion))
-		}
 		if intVer < minimumRequiredMySQLVersion {
 			return false, fmt.Errorf("Minimum MySQL version requirements not met. Found: %s, Wanted: %s", versionString(intVer, *ss.settings.DriverName), versionString(minimumRequiredMySQLVersion, *ss.settings.DriverName))
 		}