Update branch name (master -> stable) in package documentation

[ci skip]

Author: d-torrance

M2/Macaulay2/packages/MultiprojectiveVarieties.m2

@@ -39,10 +39,10 @@ requiredCremonaVersion := "5.2.1";
 if Cremona.Options.Version < requiredCremonaVersion then (
     <<endl<<"Your version of the Cremona package is outdated (required version "<<requiredCremonaVersion<<" or newer);"<<endl;
     <<"you can manually download the latest version from"<<endl;
-    <<"https://github.com/Macaulay2/M2/tree/master/M2/Macaulay2/packages."<<endl;
+    <<"https://github.com/Macaulay2/M2/tree/stable/M2/Macaulay2/packages."<<endl;
     <<"To automatically download the latest version of Cremona in your current directory,"<<endl;
     <<"you may run the following Macaulay2 code:"<<endl<<"***"<<endl<<endl;
-    <<///(makeDirectory("Cremona"), for f in {"Cremona.m2","Cremona/documentation.m2","Cremona/examples.m2","Cremona/tests.m2"} do run("curl -s -o "|f|" https://raw.githubusercontent.com/Macaulay2/M2/master/M2/Macaulay2/packages/"|f));///<<endl<<endl<<"***"<<endl;
+    <<///(makeDirectory("Cremona"), for f in {"Cremona.m2","Cremona/documentation.m2","Cremona/examples.m2","Cremona/tests.m2"} do run("curl -s -o "|f|" https://raw.githubusercontent.com/Macaulay2/M2/stable/M2/Macaulay2/packages/"|f));///<<endl<<endl<<"***"<<endl;
     error("required Cremona package version "|requiredCremonaVersion|" or newer");
 );
 

M2/Macaulay2/packages/NCAlgebra/NCAlgebraDoc.m2

@@ -39,7 +39,7 @@ doc ///
 
       Detailed instructions for installing Bergman, as well as the NCAlgebra system, can be
       found in the file installNCAlgebra.txt file contained in the NCAlgebra package directory.
-      It may also be found at @HREF"https://github.com/Macaulay2/M2/blob/master/M2/Macaulay2/packages/NCAlgebra/installNCAlgebra.txt"@.
+      It may also be found at @HREF"https://github.com/Macaulay2/M2/blob/stable/M2/Macaulay2/packages/NCAlgebra/installNCAlgebra.txt"@.
 
   Subnodes
     "Basic operations on noncommutative algebras"
@@ -4116,7 +4116,7 @@ doc ///
       Text
          Detailed instructions for installing Bergman, as well as the NCAlgebra system, can be
 	 found in the file installNCAlgebra.txt file contained in the NCAlgebra package directory.
-	 It may also be found at @HREF"https://github.com/Macaulay2/M2/blob/master/M2/Macaulay2/packages/NCAlgebra/installNCAlgebra.txt"@.
+	 It may also be found at @HREF"https://github.com/Macaulay2/M2/blob/stable/M2/Macaulay2/packages/NCAlgebra/installNCAlgebra.txt"@.
    SeeAlso
       "Using the Bergman interface"
 ///