Update AppContext.BaseDirectory and AppDomain.BaseDirectory summaries (#12877)

* Update AppContext.BaseDirectory and AppDomain.BaseDirectory summaries per runtime#41341

* Remove single-file app remarks from AppContext.BaseDirectory and AppDomain.BaseDirectory

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

xml/System/AppContext.xml

@@ -169,15 +169,9 @@ If you set the same switch in more than one way, the order of precedence for det
         <ReturnType>System.String</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets the file path of the base directory that the assembly resolver uses to probe for assemblies.</summary>
-        <value>The file path of the base directory that the assembly resolver uses to probe for assemblies.</value>
-        <remarks>
-          <format type="text/markdown"><![CDATA[
-
-For bundled assemblies, the value returned is the containing directory of the host executable.
-
- ]]></format>
-        </remarks>
+        <summary>Gets the file path of the base directory of the application.</summary>
+        <value>The file path of the base directory of the application.</value>
+        <remarks>To be added.</remarks>
       </Docs>
     </Member>
     <Member MemberName="GetData">

xml/System/AppDomain.xml

@@ -347,8 +347,8 @@ The <xref:System.ResolveEventArgs.RequestingAssembly?displayProperty=nameWithTyp
         <ReturnType>System.String</ReturnType>
       </ReturnValue>
       <Docs>
-        <summary>Gets the base directory that the assembly resolver uses to probe for assemblies.</summary>
-        <value>The base directory that the assembly resolver uses to probe for assemblies.</value>
+        <summary>Gets the base directory of the application.</summary>
+        <value>The base directory of the application.</value>
         <remarks>
           <format type="text/markdown"><![CDATA[