[clang][docs] Fix documentation of -O
D79916 changed the behaviour from -O2 to -O1 but the documentation was
not updated to reflect this.
(cherry picked from commit 788c7d2ec11dfc868a5b03478c922dc9699c6d47)
diff --git a/clang/docs/CommandGuide/clang.rst b/clang/docs/CommandGuide/clang.rst
index 2cca04f..2dfeafd 100644
--- a/clang/docs/CommandGuide/clang.rst
+++ b/clang/docs/CommandGuide/clang.rst
@@ -385,7 +385,7 @@
:option:`-Og` Like :option:`-O1`. In future versions, this option might
disable different optimizations in order to improve debuggability.
- :option:`-O` Equivalent to :option:`-O2`.
+ :option:`-O` Equivalent to :option:`-O1`.
:option:`-O4` and higher
