Doc: Fix typos spotted by @yurchor

doc/classes/ConfigFile.xml

@@ -117,7 +117,7 @@
 			<argument index="2" name="value" type="Variant">
 			</argument>
 			<description>
-				Assigns a value to the specified key of the the specified section. If the section and/or the key do not exist, they are created. Passing a [code]null[/code] value deletes the specified key if it exists, and deletes the section if it ends up empty once the key has been removed.
+				Assigns a value to the specified key of the specified section. If the section and/or the key do not exist, they are created. Passing a [code]null[/code] value deletes the specified key if it exists, and deletes the section if it ends up empty once the key has been removed.
 			</description>
 		</method>
 	</methods>

doc/classes/PrismMesh.xml

@@ -14,7 +14,7 @@
 	</methods>
 	<members>
 		<member name="left_to_right" type="float" setter="set_left_to_right" getter="get_left_to_right">
-			Displacement of of the upper edge along the x-axis. 0.0 positions edge straight above the bottome left edge. Defaults to 0.5 (positioned on the midpoint).
+			Displacement of the upper edge along the x-axis. 0.0 positions edge straight above the bottome left edge. Defaults to 0.5 (positioned on the midpoint).
 		</member>
 		<member name="size" type="Vector3" setter="set_size" getter="get_size">
 			Size of the prism. Defaults to (2.0, 2.0, 2.0).

doc/classes/SpriteFrames.xml

@@ -17,7 +17,7 @@
 			<argument index="0" name="anim" type="String">
 			</argument>
 			<description>
-				Adds a new animation to the the library.
+				Adds a new animation to the library.
 			</description>
 		</method>
 		<method name="add_frame">