change based on lindsey's feedback

(cherry picked from commit 9e822ac)

Author: shuangela

source/usage-examples.txt

@@ -23,7 +23,7 @@ Usage Examples
    Write Operations </usage-examples/write-operations>
    Bulk Operations </usage-examples/bulkWrite>
    Monitor Data Changes </usage-examples/changestream>
-   Count Documents Usage Example </usage-examples/count>
+   Count Documents Method Example </usage-examples/count>
    Distinct Field Values </usage-examples/distinct>
    Run a Command </usage-examples/command>
    Use Struct Tags </usage-examples/struct-tagging>

source/usage-examples/count.txt

@@ -1,7 +1,7 @@
 .. _golang-count-usage-example:
 
 =============================
-Count Documents Usage Example
+Count Documents Method Example
 =============================
 
 .. default-domain:: mongodb