change language to refer to starred transactions (#5850)

Changed most instances of the word "key" (except for one) to match UI better

Author: imatwawana

src/docs/product/performance/transaction-summary.mdx

@@ -143,9 +143,9 @@ Spans with the same operation and description are grouped together into a single
 
 ## Additional Actions
 
-### Starring Key Transactions
+### Starring Important Transactions {#starring-key-transactions}
 
-If you find an important transaction you want to return to, click "Star for Team" in the upper right corner and mark it as a key transaction for any of your teams. This will be saved so you can view this from your [Performance Homepage](/product/performance/). The key transactions you mark will be shared with members of the same team and each team can have up to 100 key transactions.
+If you find an important transaction you want to return to, click "Star for Team" in the upper right corner to mark it as a key transaction for any of your teams. This will be saved so you can view this from your [Performance Homepage](/product/performance/). The transactions you star will be shared with members of the same team and each team can have up to 100 starred transactions.
 
 ### Creating Alerts