Typo Update Private-Txns-Migration.md (#7870)

The phrase "private transaction created using v1.3.4" should be in the plural form: "private transactions created using v1.3.4".

Corrected.

Signed-off-by: Dmitry <98899785+mdqst@users.noreply.github.com>
Co-authored-by: Sally MacFarlane <macfarla.github@gmail.com>

docs/Private-Txns-Migration.md

@@ -12,7 +12,7 @@ state storage when upgrading to v1.4. It is not possible to upgrade to v1.4 with
 ## Private transactions created using v1.3.4 or earlier 
 
 A critical issue for privacy users with private transactions created using Hyperledger Besu v1.3.4 
-or earlier has been identified. If you have a network with private transaction created using v1.3.4 
+or earlier has been identified. If you have a network with private transactions created using v1.3.4 
 or earlier, please read the following and take the appropriate steps: 
 
 https://wiki.hyperledger.org/display/BESU/Critical+Issue+for+Privacy+Users 
@@ -41,4 +41,4 @@ your Besu database from backup and restart the migration process.
 ## Migration support 
 
 If you have a long running network with a large volume of private transactions and/or would like to discuss
-the migration process with us before upgrading, contact us at support@pegasys.tech  
+the migration process with us before upgrading, contact us at support@pegasys.tech