[llvm] Make some fixes to the LLVM Language Ref. (PR #137782)

[Kip Hamiltons via llvm-commits]

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@@ -727,7 +727,7 @@ optimizations based on the 'constantness' are valid for the translation
 units that do not include the definition.
 
 As SSA values, global variables define pointer values that are in scope
-(i.e. they dominate) all basic blocks in the program. Global variables
+for (i.e. they dominate) all basic blocks in the program. Global variables
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KipHamiltons wrote:

We should be able to read this sentence without the parenthesised words, but we can't without adding `for`.

https://github.com/llvm/llvm-project/pull/137782