revert transcriptContainer change from pull/557 (#679)

RE https://sourcegraph.slack.com/archives/C05AGQYD528/p1692045809151649

this PR is to revert changes made to the transcript container CSS class
that caused the position of the chat input box to be moved in
#557:


![image](https://github.com/sourcegraph/cody/assets/68532117/99bcfa81-3140-4f37-8481-b29b17561af1)


## Test plan

<!-- Required. See
https://docs.sourcegraph.com/dev/background-information/testing_principles.
-->

### After 

![image](https://github.com/sourcegraph/cody/assets/68532117/f8a2e3aa-5d7b-44e7-b0c5-1f4c6b26532c)

lib/ui/src/Chat.module.css

@@ -4,6 +4,10 @@
     height: 100%;
 }
 
+.transcript-container {
+    flex: 1;
+}
+
 .input-row {
     position: relative;
     display: flex;

lib/ui/src/Chat.tsx

@@ -371,7 +371,7 @@ export const Chat: React.FunctionComponent<ChatProps> = ({
                     humanTranscriptItemClassName={humanTranscriptItemClassName}
                     transcriptItemParticipantClassName={transcriptItemParticipantClassName}
                     transcriptActionClassName={transcriptActionClassName}
-                    className={!isGettingStartedComponentVisible ? 'flex-1' : undefined}
+                    className={styles.transcriptContainer}
                     textAreaComponent={TextArea}
                     EditButtonContainer={EditButtonContainer}
                     editButtonOnSubmit={editButtonOnSubmit}