docs: fixes small typo in README.md (testing-library#152)

Hey, this fixes small typo in `README.md` in function parameters example for `getText`.

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**What**:

Documentation typo.

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**Why**:

So documentation is more precise :)

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Author: Łukasz Mazurek

README.md

@@ -794,7 +794,7 @@ affect the precision of string matching:
 
 // Matching a string:
 getByText(container, 'Hello World') // full string match
-getByText(container, 'llo Worl'), {exact: false} // substring match
+getByText(container, 'llo Worl', {exact: false}) // substring match
 getByText(container, 'hello world', {exact: false}) // ignore case
 
 // Matching a regex: