Update Doc/library/string.templatelib.rst

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Author: davepeck

Doc/library/string.templatelib.rst

@@ -258,7 +258,7 @@ Types
    .. attribute:: expression
       :type: str
 
-      For interpolations created from t-string literals, :attr:`!expression`
+      For interpolations created by t-string literals, :attr:`!expression`
       is the source text found inside the curly braces, including any
       whitespace, but excluding the curly braces themselves. For manually
       created interpolations, :attr:`!expression` is an arbitrary string.