Fix " to ' on new variable. Sed is broken. Update Dockerfile to v1.2

docker/Dockerfile

@@ -1,6 +1,6 @@
 FROM ubuntu:22.04
 
-LABEL dockerfile.version="v1.1" dockerfile.release-date="2023-01-03"
+LABEL dockerfile.version="v1.2" dockerfile.release-date="2023-01-04"
 
 # Set up ENVs that will be utilized in compose file.
 ENV TZ Etc/UTC

settings_update.php

@@ -6,7 +6,7 @@ include("database_version.php");
 <?php
 
 //fetch the latest code changes but don't apply them\
-$repo_branch = "master";
+$repo_branch = 'master';
 exec("git fetch", $output, $result);
 $latest_version = exec("git rev-parse origin/$repo_branch");
 $current_version = exec("git rev-parse HEAD");