Remove unneeded backslash ESCAPE from LIKE translations (#3103)

Fixes #3085

Author: roji

src/EFCore.PG/Query/Internal/NpgsqlSqlTranslatingExpressionVisitor.cs

@@ -456,8 +456,7 @@ when patternParameter.Name.StartsWith(QueryCompilationContext.QueryParameterPref
 
                 translation = _sqlExpressionFactory.Like(
                     translatedInstance,
-                    new SqlParameterExpression(escapedPatternParameter.Name!, escapedPatternParameter.Type, stringTypeMapping),
-                    _sqlExpressionFactory.Constant(LikeEscapeChar.ToString()));
+                    new SqlParameterExpression(escapedPatternParameter.Name!, escapedPatternParameter.Type, stringTypeMapping));
 
                 return true;
             }

test/EFCore.PG.FunctionalTests/Query/CitextQueryTest.cs

@@ -48,7 +48,7 @@ public void StartsWith_param_pattern()
 
 SELECT s."Id", s."CaseInsensitiveText"
 FROM "SomeEntities" AS s
-WHERE s."CaseInsensitiveText" LIKE @__param_0_startswith ESCAPE '\'
+WHERE s."CaseInsensitiveText" LIKE @__param_0_startswith
 LIMIT 2
 """);
     }
@@ -102,7 +102,7 @@ public void EndsWith_param_pattern()
 
 SELECT s."Id", s."CaseInsensitiveText"
 FROM "SomeEntities" AS s
-WHERE s."CaseInsensitiveText" LIKE @__param_0_endswith ESCAPE '\'
+WHERE s."CaseInsensitiveText" LIKE @__param_0_endswith
 LIMIT 2
 """);
     }
@@ -156,7 +156,7 @@ public void Contains_param_pattern()
 
 SELECT s."Id", s."CaseInsensitiveText"
 FROM "SomeEntities" AS s
-WHERE s."CaseInsensitiveText" LIKE @__param_0_contains ESCAPE '\'
+WHERE s."CaseInsensitiveText" LIKE @__param_0_contains
 LIMIT 2
 """);
     }