Fix difference symbol from lower-case to uppercase Delta

Author: dietmarw

OpenIPSL/UsersGuide/Conventions.mo

@@ -13,7 +13,7 @@ Here are some naming conventions that we try to obey:
 <li> Names of the parameters and variables should correspond to those found in the respective documentation.</li>
 <li> Subscript should be denoted in Modelica with underscore, e.g., <code>T_r</code>
 or <code>K_1</code>. <strong>Note:</strong> some parameter names have first upper case letters and others lower case.</li>
-<li> Deviation signals such as &delta;&omega;, should be written as <code>domega</code> in Modelica.</li>
+<li> Deviation signals such as &Delta;&omega;, should be written as <code>domega</code> in Modelica.</li>
 <li> Parameters which are not to be entered by user and variables which are not to be seen by users should be <strong>protected</strong>.</li>
 <li> Parameters and variables should be declared as their specific type such as <code>Types.ApparentPower</code>
 for variables that are declared in MVA. <strong>Note:</strong> if the proper unit is not represented in