Decrease the number of builds compared during mixed mode to the most recent 10 (#3289)

This decreases the maximum number of builds we will compare during mixed
mode testing from 50 to 10. (Note that we didn't actually have 50
versions that were mixed-mode testing compatible as it required
4.0.559.0, but we do have more than 10.) This is in response to release
build failures (see:
https://github.com/FoundationDB/fdb-record-layer/actions/runs/14217433940
and
https://github.com/FoundationDB/fdb-record-layer/actions/runs/14222485395).
Those appear to have been caused by the mixed mode test job running out
of resources, as it started experiencing timeouts and didn't fail
locally. The hope is that decreasing this number makes the run able to
complete.

We may need to consider adjusting this in the future to be smarter
(e.g., comparing the most recent version to all versions in the this and
the previous minor version, as those should be the primary candidates
for upgrades), but that's something we could think about later. There
are already (intentaional) incompatibilities between the current 4.2
version and the 4.0 versions that make up the majority of the versions
that will currently be excluded by this change, and so continuing to
validate that those are incompatible is probably of little value.

Author: alecgrieser

yaml-tests/yaml-tests.gradle

@@ -142,7 +142,7 @@ static def getAttributesFromJar(File file) {
 ext.resolveManyServers = { ->
     Set<File> selectedServers = new HashSet<>();
     Set<String> rejectedVersions = new HashSet<>();
-    while (selectedServers.size() < 50) {
+    while (selectedServers.size() < 10) {
         def serverFile = resolveOtherServer(rejectedVersions)
         def attributes = getAttributesFromJar(serverFile)
         // 4.0.559.0 is the first version that introduced the server, so we won't be able to find anything