Fix heading levels in upgrade instructions

Author: seancolsen

docs/docs/administration/upgrade/0.1.5.md

@@ -1,6 +1,6 @@
 # Upgrade Mathesar to 0.1.5
 
-### For installations using Docker Compose
+## For installations using Docker Compose
 
 If you have a Docker compose installation (including one from the guided script), run the command below:
 
@@ -12,6 +12,6 @@ docker compose -f /etc/mathesar/docker-compose.yml up --pull always -d
     You may need to change `/etc/mathesar/` in the command above if you chose to install Mathesar to a different directory.
 
 
-### For installations done from scratch
+## For installations done from scratch
 
 If you installed from scratch, the upgrade instructions are the same as [for 0.1.4](./0.1.4.md#scratch), except that you'll need to specify version 0.1.5 when pulling code from the repository in Step 2. You should also skip Step 5 – you do not need to change the environment variables.

docs/docs/administration/upgrade/0.1.6.md

@@ -1,6 +1,6 @@
 # Upgrade Mathesar to 0.1.6
 
-### For installations using Docker Compose
+## For installations using Docker Compose
 
 If you have a Docker compose installation (including one from the guided script), run the command below:
 
@@ -12,7 +12,7 @@ docker compose -f /etc/mathesar/docker-compose.yml up --pull always -d
     You may need to change `/etc/mathesar/` in the command above if you chose to install Mathesar to a different directory.
 
 
-### For installations done from scratch
+## For installations done from scratch
 
 If you installed Mathesar [from scratch](../../installation/build-from-source/index.md), then use these steps to upgrade your installation to 0.1.6.
 

docs/docs/administration/upgrade/0.1.7.md

@@ -1,6 +1,6 @@
 # Upgrade Mathesar to 0.1.7
 
-### For installations using Docker Compose
+## For installations using Docker Compose
 
 If you have a Docker compose installation (including one from the guided script), run the command below:
 
@@ -12,7 +12,7 @@ docker compose -f /etc/mathesar/docker-compose.yml up --pull always -d
     You may need to change `/etc/mathesar/` in the command above if you chose to install Mathesar to a different directory.
 
 
-### For installations done from scratch
+## For installations done from scratch
 
 If you installed Mathesar [from scratch](../../installation/build-from-source/index.md), then use these steps to upgrade your installation to 0.1.7.