Fix constructor reference sidebar title to stagehand() (#1178)

# why

link fix 

# what changed

# test plan

Co-authored-by: Steven Bryan <[email protected]>

Author: rsbryan

docs/docs.json

@@ -101,7 +101,7 @@
       {
         "group": "Reference",
         "pages": [
-          "references/Stagehand",
+          "references/constructor",
           "references/act",
           "references/extract",
           "references/observe",

docs/references/constructor.mdx

@@ -1,5 +1,5 @@
 ---
-title: Stagehand Constructor
+title: 'stagehand()'
 description: 'Complete API reference for initializing Stagehand'
 icon: 'hammer'
 ---