Rename master to main for plone.api

Author: stevepiercy

.gitmodules

@@ -9,4 +9,4 @@
 [submodule "submodules/plone.api"]
 	path = submodules/plone.api
 	url = https://github.com/plone/plone.api.git
-	branch = master
+	branch = main

docs/contributing/documentation/admins.md

@@ -226,7 +226,7 @@ Only members of the Plone Documentation Team should update git submodules from t
     git pull
     # plone.api
     cd submodules/plone.api
-    git checkout master
+    git checkout main
     git pull
     # plone.restapi
     cd ../../submodules/plone.restapi

docs/contributing/documentation/index.md

@@ -74,7 +74,7 @@ Plone documentation consists of several repositories.
 When you {doc}`setup and build <setup-build>` the documentation, it will automatically pull in the other repositories via git submodules.
 
 ```{important}
-We currently use the branches `plone/documentation@6.0`, `plone/plone.api@master`, `plone/plone.restapi@main`, and `plone/volto@main` as the default branches for developing Plone 6 Documentation.
+We currently use the branches `plone/documentation@6.0`, `plone/plone.api@main`, `plone/plone.restapi@main`, and `plone/volto@main` as the default branches for developing Plone 6 Documentation.
 ```
 
 
@@ -208,10 +208,6 @@ You already imported the external repositories into the `plone/documentation` re
     You might need to resolve conflicts.
 
     ```shell
-    # for plone.api
-    git checkout master
-
-    # for plone.restapi or volto
     git checkout main
     
     # pull in the latest changes

docs/contributing/first-time.md

@@ -201,7 +201,7 @@ _Plone git workflow_
 
 Once you have your environment set up, then you can follow standard best practices for working with git.
 
-In the following command examples, we will use `main` as the default branch, although `master` may still be in use for some repositories.
+In the following command examples, you should use `main` as the default branch, although `master` may still be in use for some repositories.
 
 Always start by checking out the default branch then update the default branch.