test: increase enoughTestMem to 1.75 Gb

PR-URL: nodejs/node#16374
Fixes: nodejs/node#16354
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/common/index.js

@@ -53,7 +53,7 @@ exports.isFreeBSD = process.platform === 'freebsd';
 exports.isLinux = process.platform === 'linux';
 exports.isOSX = process.platform === 'darwin';
 
-exports.enoughTestMem = os.totalmem() > 0x40000000; /* 1 Gb */
+exports.enoughTestMem = os.totalmem() > 0x70000000; /* 1.75 Gb */
 const cpus = os.cpus();
 exports.enoughTestCpu = Array.isArray(cpus) &&
                         (cpus.length > 1 || cpus[0].speed > 999);