Update base branch conditionally in button click event

The button click event was modified to show a modal only if a certain condition is not met; otherwise, it will immediately update the base branch. The condition depends on the state of the `mergeUpstreamWarningDismissed` variable. 

Changes:
- Replaced the direct function call `updateTargetModal.show` upon button click with a conditional function.
- Now, on button click, if `mergeUpstreamWarningDismissed` is true, the base branch gets updated using `branchController.updateBaseBranch()`.
- If `mergeUpstreamWarningDismissed` is false, the previous functionality remains, i.e., `updateTargetModal.show` gets called

src/routes/repo/[projectId]/BaseBranchPeek.svelte

@@ -43,7 +43,13 @@
 							width="full-width"
 							height="small"
 							color="purple"
-							on:click={updateTargetModal.show}
+							on:click={() => {
+								if ($mergeUpstreamWarningDismissed) {
+									branchController.updateBaseBranch();
+								} else {
+									updateTargetModal.show;
+								}
+							}}
 						>
 							Merge into common base
 						</Button>