Issue#1503: Doc typo corrections.

Author: JHertz5

docs/signal_rules.rst

@@ -339,7 +339,7 @@ signal_018
 
 |phase_1| |error| |structure|
 
-This rule checks the **:=** is on the same line at the **signal** keyword.
+This rule checks the **:=** is on the same line as the **signal** keyword.
 
 **Violation**
 

vsg/rules/signal/rule_018.py

@@ -9,7 +9,7 @@
 
 class rule_018(Rule):
     """
-    This rule checks the **:=** is on the same line at the **signal** keyword.
+    This rule checks the **:=** is on the same line as the **signal** keyword.
 
     **Violation**