Fix accidental Npgsql version upgrade (#228)

Author: Arkatufus

src/Directory.Build.props

@@ -19,7 +19,7 @@
     <AkkaVersion>1.5.13</AkkaVersion>
 
     <!-- Install from version 5.0.11 included all the way up to 7.x.x, but don't go up a major version -->
-    <PostgresLowVersion>7.0.6</PostgresLowVersion>
+    <PostgresLowVersion>5.0.11</PostgresLowVersion>
     <PostgresHighVersion>8</PostgresHighVersion>
     <PostgresVersion>[$(PostgresLowVersion), $(PostgresHighVersion))</PostgresVersion>
   </PropertyGroup>