Fix typo in PerformanceManager README

Change-Id: I16dd76160de8cec0642f395a87acb2191ba38733
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1894419
Auto-Submit: Oliver Li <olivierli@chromium.org>
Commit-Queue: Chris Hamilton <chrisha@chromium.org>
Reviewed-by: Chris Hamilton <chrisha@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712124}

components/performance_manager/README.md

@@ -2,7 +2,7 @@
 
 The Performance Manager centralizes policy for data-driven resource management
 and planning. Central to this is the [graph](graph/graph_impl.h) which is
-comprised of nodes that reflect a the course structure of a browser at the
+comprised of nodes that reflect the coarse structure of a browser at the
 level of [pages](graph/page_node_impl.h), [frames](graph/frame_node_impl.h)
 [processes](graph/process_node_impl.h) and so forth. Each node is adorned with
 relationships and properties sufficient to allow performance management policy