backend: fix typos found by codespell

backend/azureblob/azureblob.go

@@ -690,7 +690,7 @@ func NewFs(ctx context.Context, name, root string, m configmap.Mapper) (fs.Fs, e
 		}
 		cred, err = azidentity.NewDefaultAzureCredential(&options)
 		if err != nil {
-			return nil, fmt.Errorf("create azure enviroment credential failed: %w", err)
+			return nil, fmt.Errorf("create azure environment credential failed: %w", err)
 		}
 	case opt.UseEmulator:
 		if opt.Account == "" {

backend/local/metadata_linux.go

@@ -91,7 +91,7 @@ func readMetadataFromFileFstatat(o *Object, m *fs.Metadata) (err error) {
 		// The types of t.Sec and t.Nsec vary from int32 to int64 on
 		// different Linux architectures so we need to cast them to
 		// int64 here and hence need to quiet the linter about
-		// unecessary casts.
+		// unnecessary casts.
 		//
 		// nolint: unconvert
 		m.Set(key, time.Unix(int64(t.Sec), int64(t.Nsec)).Format(metadataTimeFormat))

backend/mega/mega.go

@@ -90,7 +90,7 @@ permanently delete objects instead.`,
 MEGA uses plain text HTTP connections by default.
 Some ISPs throttle HTTP connections, this causes transfers to become very slow.
 Enabling this will force MEGA to use HTTPS for all transfers.
-HTTPS is normally not necesary since all data is already encrypted anyway.
+HTTPS is normally not necessary since all data is already encrypted anyway.
 Enabling it will increase CPU usage and add network overhead.`,
 			Default:  false,
 			Advanced: true,