Change API docs schedule from monthly to every 2 weeks (microsoft#22524)

### Description
<!-- Describe your changes. -->
Current API docs workflows are scheduled to run monthly, but artifacts
expire after 30 days, which could create issues for 31-day months.
Updating to regenerate artifacts every 2 weeks.


### Motivation and Context
<!-- - Why is this change required? What problem does it solve?
- If it fixes an open issue, please link to the issue here. -->

.github/workflows/publish-c-apidocs.yml

@@ -9,7 +9,7 @@ on:
       - include/onnxruntime/core/session/**
       - orttraining/orttraining/training_api/include/**
   schedule:
-    - cron: '0 0 1 * *'
+    - cron: '0 0 1,15 * *'
   workflow_dispatch:
 
 concurrency:

.github/workflows/publish-csharp-apidocs.yml

@@ -8,7 +8,7 @@ on:
     paths:
       - csharp/**
   schedule:
-    - cron: '0 0 1 * *'
+    - cron: '0 0 1,15 * *'
   workflow_dispatch:
 
 concurrency:

.github/workflows/publish-java-apidocs.yml

@@ -8,7 +8,7 @@ on:
     paths:
       - java/**
   schedule:
-    - cron: '0 0 1 * *'
+    - cron: '0 0 1,15 * *'
   workflow_dispatch:
 
 concurrency:

.github/workflows/publish-js-apidocs.yml

@@ -8,7 +8,7 @@ on:
     paths:
       - js/common/**
   schedule:
-    - cron: '0 0 1 * *'
+    - cron: '0 0 1,15 * *'
   workflow_dispatch:
 
 concurrency:

.github/workflows/publish-objectivec-apidocs.yml

@@ -8,7 +8,7 @@ on:
     paths:
     - objectivec/**
   schedule:
-  - cron: '0 0 1 * *'
+  - cron: '0 0 1,15 * *'
   workflow_dispatch:
 
 concurrency:

.github/workflows/publish-python-apidocs.yml

@@ -9,7 +9,7 @@ on:
       - onnxruntime/python/**
       - docs/python/**
   schedule:
-    - cron: '0 0 1 * *'
+    - cron: '0 0 1,15 * *'
   workflow_dispatch:
 
 concurrency: